Model: iPhone XS Max
Issues since 14.1, currently 14.2:
cellular data: not at all or very slow upload speeds (less than 1 mbs), not at all or sometime good/very download speeds (0 or 250 mbs).
calls without wifi calling toggle active can get disconnected during the call or the other person cannot hear me while I can hear that person very well.
Carrier signal is at max level (4 bars) and there are no apparent issues with wifi or bluetooth.
I did everything! Literally check every possible root cause:
The carrier:
Physical sims/ e-sims
Same sims in samsung worked like a charm
Different carriers for each sim
All having the same problem
The phone:
More than 5 hours with apple support on the line
Went through all the steps (up to complete restore) and sent the full 30 mins diagnostics
Conclusion: no hardware / software problem
Recommendation: go to an authorized apple service provider
Did that, but they also didn’t find the problem (unofficial/ personal from them: ios-related)
Installed the 14.3 beta 1 and 2, same problem
Since not everyone with XS Max is having this issue, I suppose something that I did may have caused this, and I have two things in mind: 1. Phone had ios 14 beta installed since it went public around June. 2. Always had a mdm profile installed for running work-related apps (and yes, of course I removed it when doing the tests).
I really believe this to be an iOS related issue and I hope the engineering team is on top of it.