January/february last year I, same as so many other people, suddenly started having issues with VoWIFI. Random disconnects after roughly 2 mins call, then when attempting to reconnect the call was ended either immediately or within a couple mins ago. If I tried switch over to VoLTE I could hear the other end but my microphone was turned off (yes, all microphones, not just phone or BT), and call was automatically ended after exactly (?) 20 seconds.
Everybody and their dogs said it was user error or errors in the carrier net. Yet noone could find any correlation. Juggling settings surrounding WIFI, VoWIFI, 5G, etc, could sometimes seem like fix the issues until we just used the phone for long enough. Nothing helped. The problems also happened over too many carriers too widespread across the world.
For me these issues ended immediately when I got a new SIM card. I thought maybe it was because my old SIM card was >10y old. Either way didn't matter to me at that point. The problem was suddenly fixed.
Fast forward to end of january / start of february, and ALL these EXACT SAME issues started again. And yes, it happened at the mostly exact time as previous year.
None of any of last year's tricks helped at all. Until I tried something new: Clear storage for the app "SIM Toolkit", and then restarted the phone. Suddenly all the call issues were gone, at least so far. TBD if it stays like that over time.
Now the question is why... Both if this is the only thing that happened when I deleted the data, and why did the problem reoccur at the same time as last year.
What happens every year at the end of january? Is it the first big update since the new Android release in fall previous year? Something else that usually is done and updated every january? I read GOS is doing a major overhaul now, and SMS notification sound and other stuff fell into a bottomless pit, but maybe not related since call issues also happens on stock Android.
Did someone regress a bugfix for all these call issues?
Did the "SIM Toolkit" data corrupt from other reasons?
Did clearing storage for "SIM Toolkit" cause another process to happen which fixed the issues via other mechanics?
Keep in mind this is not only happening on GOS. Also on stock Android. In any way, it's really on high time this issue was fixed once and for all, and buried far down into red hot magma.