When I open the following page in Chrome on my iphone everything works fine
https://forkphorus.github.io/app.html?id=673890545
Instead, if I open the page inside a webviewer component and I open the app in MIT App Inventor 2 Companion, after a little while I get an error message saying that "An Internal error occurred".
Try https://gallery.appinventor.mit.edu/?galleryid=386dd4c4-421b-43ef-b0a8-2fe24608f073 in MIT Companion.