IOS BUG FIX: VOIP VIDEO CALL APP (URGENT)

Hi, we are an intercom company that manufactures hardware that makes video calls to an ios app.

The app receives the video calls, and it runs on linphone client. (one way video calls, intercom to app)
The app is written in SWIFT.

For our iOS app, we have some users having an issue loading the video call correctly.
it hangs at the loading screen and video does not load. (only affects some users, probably 1-2% of users)

We found out that this issue gets solved with voLTE turned off. (temporary solution)
However, the app should work, regardless of volte status.
We would like this issue to be fixed asap.

Do let me know if you are interested. Thank you.

APP LINK: https://apps.apple.com/us/app/schonell-interphone/id1171733979

Enclosed video of problem.