Web portal - moves with the camera

I tried to use the project on the art portal https://forum.zap.works/t/sipsmith-portal-inspiration-project/3463 . When browsing through the zappar application, everything works fine, but for some reason the web portal does not stand still and moves with the camera. What could be wrong? Maybe someone has encountered a similar bug?
Is it possible that the web ar zappar does not support trolls?

If you’re using WebAR, it handles world tracked experiences a bit differently. WebAR uses something called Instant Tracking. While there are some updates and improvements coming to Instant Tracking soon, it is not currently suited to experiences where the user is looking away from the initial placement point.

I imagine what you’re experiencing is Zappar’s WebAR not being able to properaly use Instant Tracking as it is losing sight of the original anchor. To compensate, a new anchor is picked that is close to the original, but still on screen, thus causing it to move with the camera.