Script error (React)

Hey Hannes,

when visiting the plugin’s settings page, the following script errors are shown:

Uncaught TypeError: R(...) is undefined
    B https://my-site.loc/wp-content/plugins/wp-html-mail/template-designer/build/index.js?ver=821ed061d9bbff0007fc:1
    renderWithHooks https://my-site.loc/wp-includes/js/dist/vendor/react-dom.js?ver=17.0.1:15015
    mountIndeterminateComponent https://my-site.loc/wp-includes/js/dist/vendor/react-dom.js?ver=17.0.1:17841
    beginWork https://my-site.loc/wp-includes/js/dist/vendor/react-dom.js?ver=17.0.1:19079
    callCallback https://my-site.loc/wp-includes/js/dist/vendor/react-dom.js?ver=17.0.1:3942
    invokeGuardedCallbackDev https://my-site.loc/wp-includes/js/dist/vendor/react-dom.js?ver=17.0.1:3991
    invokeGuardedCallback https://my-site.loc/wp-includes/js/dist/vendor/react-dom.js?ver=17.0.1:4053
    beginWork$1 https://my-site.loc/wp-includes/js/dist/vendor/react-dom.js?ver=17.0.1:23994
    performUnitOfWork https://my-site.loc/wp-includes/js/dist/vendor/react-dom.js?ver=17.0.1:22806
    workLoopSync https://my-site.loc/wp-includes/js/dist/vendor/react-dom.js?ver=17.0.1:22737
    renderRootSync https://my-site.loc/wp-includes/js/dist/vendor/react-dom.js?ver=17.0.1:22700
    performSyncWorkOnRoot https://my-site.loc/wp-includes/js/dist/vendor/react-dom.js?ver=17.0.1:22323
    flushSyncCallbackQueueImpl https://my-site.loc/wp-includes/js/dist/vendor/react-dom.js?ver=17.0.1:11357
    unstable_runWithPriority https://my-site.loc/wp-includes/js/dist/vendor/react.js?ver=17.0.1:2764
    runWithPriority$1 https://my-site.loc/wp-includes/js/dist/vendor/react-dom.js?ver=17.0.1:11306
    flushSyncCallbackQueueImpl https://my-site.loc/wp-includes/js/dist/vendor/react-dom.js?ver=17.0.1:11352
    flushSyncCallbackQueue https://my-site.loc/wp-includes/js/dist/vendor/react-dom.js?ver=17.0.1:11339
    scheduleUpdateOnFiber https://my-site.loc/wp-includes/js/dist/vendor/react-dom.js?ver=17.0.1:21923
    dispatchAction https://my-site.loc/wp-includes/js/dist/vendor/react-dom.js?ver=17.0.1:16169
    ue https://my-site.loc/wp-content/plugins/wp-html-mail/template-designer/build/index.js?ver=821ed061d9bbff0007fc:1
    promise callback*666/ue/</< https://my-site.loc/wp-content/plugins/wp-html-mail/template-designer/build/index.js?ver=821ed061d9bbff0007fc:1
    ue https://my-site.loc/wp-content/plugins/wp-html-mail/template-designer/build/index.js?ver=821ed061d9bbff0007fc:1
    invokePassiveEffectCreate https://my-site.loc/wp-includes/js/dist/vendor/react-dom.js?ver=17.0.1:23517
    callCallback https://my-site.loc/wp-includes/js/dist/vendor/react-dom.js?ver=17.0.1:3942
    invokeGuardedCallbackDev https://my-site.loc/wp-includes/js/dist/vendor/react-dom.js?ver=17.0.1:3991
    invokeGuardedCallback https://my-site.loc/wp-includes/js/dist/vendor/react-dom.js?ver=17.0.1:4053
    flushPassiveEffectsImpl https://my-site.loc/wp-includes/js/dist/vendor/react-dom.js?ver=17.0.1:23604
    unstable_runWithPriority https://my-site.loc/wp-includes/js/dist/vendor/react.js?ver=17.0.1:2764
    runWithPriority$1 https://my-site.loc/wp-includes/js/dist/vendor/react-dom.js?ver=17.0.1:11306
    flushPassiveEffects https://my-site.loc/wp-includes/js/dist/vendor/react-dom.js?ver=17.0.1:23477
    commitBeforeMutationEffects https://my-site.loc/wp-includes/js/dist/vendor/react-dom.js?ver=17.0.1:23354
    workLoop https://my-site.loc/wp-includes/js/dist/vendor/react.js?ver=17.0.1:2713
    flushWork https://my-site.loc/wp-includes/js/dist/vendor/react.js?ver=17.0.1:2686
    performWorkUntilDeadline https://my-site.loc/wp-includes/js/dist/vendor/react.js?ver=17.0.1:2453
    EventHandlerNonNull* https://my-site.loc/wp-includes/js/dist/vendor/react.js?ver=17.0.1:2476
    <anonymous> https://my-site.loc/wp-includes/js/dist/vendor/react.js?ver=17.0.1:12
    <anonymous> https://my-site.loc/wp-includes/js/dist/vendor/react.js?ver=17.0.1:13
index.js:1:35331
11:38:50.974
The above error occurred in the <B> component:

B@https://my-site.loc/wp-content/plugins/wp-html-mail/template-designer/build/index.js?ver=821ed061d9bbff0007fc:1:34355
div
div
v@https://my-site.loc/wp-content/plugins/wp-html-mail/template-designer/build/index.js?ver=821ed061d9bbff0007fc:1:6412
div
div
M@https://my-site.loc/wp-content/plugins/wp-html-mail/template-designer/build/index.js?ver=821ed061d9bbff0007fc:1:38007
div
div
TabPanel@https://my-site.loc/wp-includes/js/dist/components.js?ver=c22dbc95bc435f9eeee5:61619:7
ue@https://my-site.loc/wp-content/plugins/wp-html-mail/template-designer/build/index.js?ver=821ed061d9bbff0007fc:1:62845
g@https://my-site.loc/wp-content/plugins/wp-html-mail/template-designer/build/index.js?ver=821ed061d9bbff0007fc:1:1901

Consider adding an error boundary to your tree to customize error handling behavior.
Visit https://reactjs.org/link/error-boundaries to learn more about error boundaries. react-dom.js:20115:17
11:38:50.977
Uncaught (in promise) TypeError: R(...) is undefined
    B https://my-site.loc/wp-content/plugins/wp-html-mail/template-designer/build/index.js?ver=821ed061d9bbff0007fc:1
    renderWithHooks https://my-site.loc/wp-includes/js/dist/vendor/react-dom.js?ver=17.0.1:15015
    mountIndeterminateComponent https://my-site.loc/wp-includes/js/dist/vendor/react-dom.js?ver=17.0.1:17841
    beginWork https://my-site.loc/wp-includes/js/dist/vendor/react-dom.js?ver=17.0.1:19079
    callCallback https://my-site.loc/wp-includes/js/dist/vendor/react-dom.js?ver=17.0.1:3942
    invokeGuardedCallbackDev https://my-site.loc/wp-includes/js/dist/vendor/react-dom.js?ver=17.0.1:3991
    invokeGuardedCallback https://my-site.loc/wp-includes/js/dist/vendor/react-dom.js?ver=17.0.1:4053
    beginWork$1 https://my-site.loc/wp-includes/js/dist/vendor/react-dom.js?ver=17.0.1:23994
    performUnitOfWork https://my-site.loc/wp-includes/js/dist/vendor/react-dom.js?ver=17.0.1:22806
    workLoopSync https://my-site.loc/wp-includes/js/dist/vendor/react-dom.js?ver=17.0.1:22737
    renderRootSync https://my-site.loc/wp-includes/js/dist/vendor/react-dom.js?ver=17.0.1:22700
    performSyncWorkOnRoot https://my-site.loc/wp-includes/js/dist/vendor/react-dom.js?ver=17.0.1:22323
    flushSyncCallbackQueueImpl https://my-site.loc/wp-includes/js/dist/vendor/react-dom.js?ver=17.0.1:11357
    unstable_runWithPriority https://my-site.loc/wp-includes/js/dist/vendor/react.js?ver=17.0.1:2764
    runWithPriority$1 https://my-site.loc/wp-includes/js/dist/vendor/react-dom.js?ver=17.0.1:11306
    flushSyncCallbackQueueImpl https://my-site.loc/wp-includes/js/dist/vendor/react-dom.js?ver=17.0.1:11352
    flushSyncCallbackQueue https://my-site.loc/wp-includes/js/dist/vendor/react-dom.js?ver=17.0.1:11339
    scheduleUpdateOnFiber https://my-site.loc/wp-includes/js/dist/vendor/react-dom.js?ver=17.0.1:21923
    dispatchAction https://my-site.loc/wp-includes/js/dist/vendor/react-dom.js?ver=17.0.1:16169
    ue https://my-site.loc/wp-content/plugins/wp-html-mail/template-designer/build/index.js?ver=821ed061d9bbff0007fc:1
    promise callback*666/ue/</< https://my-site.loc/wp-content/plugins/wp-html-mail/template-designer/build/index.js?ver=821ed061d9bbff0007fc:1
    ue https://my-site.loc/wp-content/plugins/wp-html-mail/template-designer/build/index.js?ver=821ed061d9bbff0007fc:1
    invokePassiveEffectCreate https://my-site.loc/wp-includes/js/dist/vendor/react-dom.js?ver=17.0.1:23517
    callCallback https://my-site.loc/wp-includes/js/dist/vendor/react-dom.js?ver=17.0.1:3942
    invokeGuardedCallbackDev https://my-site.loc/wp-includes/js/dist/vendor/react-dom.js?ver=17.0.1:3991
    invokeGuardedCallback https://my-site.loc/wp-includes/js/dist/vendor/react-dom.js?ver=17.0.1:4053
    flushPassiveEffectsImpl https://my-site.loc/wp-includes/js/dist/vendor/react-dom.js?ver=17.0.1:23604
    unstable_runWithPriority https://my-site.loc/wp-includes/js/dist/vendor/react.js?ver=17.0.1:2764
    runWithPriority$1 https://my-site.loc/wp-includes/js/dist/vendor/react-dom.js?ver=17.0.1:11306
    flushPassiveEffects https://my-site.loc/wp-includes/js/dist/vendor/react-dom.js?ver=17.0.1:23477
    commitBeforeMutationEffects https://my-site.loc/wp-includes/js/dist/vendor/react-dom.js?ver=17.0.1:23354
    workLoop https://my-site.loc/wp-includes/js/dist/vendor/react.js?ver=17.0.1:2713
    flushWork https://my-site.loc/wp-includes/js/dist/vendor/react.js?ver=17.0.1:2686
    performWorkUntilDeadline https://my-site.loc/wp-includes/js/dist/vendor/react.js?ver=17.0.1:2453
    EventHandlerNonNull* https://my-site.loc/wp-includes/js/dist/vendor/react.js?ver=17.0.1:2476
    <anonymous> https://my-site.loc/wp-includes/js/dist/vendor/react.js?ver=17.0.1:12
    <anonymous> https://my-site.loc/wp-includes/js/dist/vendor/react.js?ver=17.0.1:13
index.js:1:35331
11:38:51.355
Warning: Can't perform a React state update on an unmounted component. This is a no-op, but it indicates a memory leak in your application. To fix, cancel all subscriptions and asynchronous tasks in a useEffect cleanup function.
g@https://my-site.loc/wp-content/plugins/wp-html-mail/template-designer/build/index.js?ver=821ed061d9bbff0007fc:1:1901

We tested w/ PHP 7.4 and 8.0, WP 5.8/6.1 and default theme and no other plugins activated but the error persists. Sporadically, the settings page is fully shown but most of the time, we only see the top nav then empty space and below that the preview pane. The tabbed settings view might show up briefly but as soon as the JS error kicks in, the UI is broken/incomplete.

Hope you can help. We could provide a test login on demand.

Regards