We did tests with another theme and your plugin worked as expected! So we contacted the Astra theme support and they did some tests also. They found out, that with your plugin activated but no “Google Analytics Tracking ID” entered everything works as expected. When adding a variation product to the cart the slide in cart appears.
When adding the tracking ID (G-…) under Woocommerce > Settings > Integration the error appears again, slide-in cart don’t show and we get the error message that I originally reported.
So I’ld like to ask if this is a known issue of the plugin or if you can help with further advice as it seems that the error is somehow plugin related?