Not compatible with GiveWP?

I’m getting an error when trying to use GiveWP on a site with Visual Subtitle installed and activated (it causes a 500 error and parts of the form won’t load).

(index):209 GET https://test.local/give/donation-form?giveDonationFormInIframe=1 500

Do you know what could be causing this? The GiveWP form works perfectly when Visual Subtitle is disabled. Thanks for any help here.