I do have an idea for the cause of the high drain. I’ve seen it on my Fairphone2 running SFOS and my Sony Xperia 10iii, I’m curious to see if others see the same.
My FP2 could run about 4 days on a full battery, it was connected to 4G. At about the time my provided switched off 3G it could only run for about a day on a full battery. Since this was a community port i did some extensive troubleshooting with the developer and we couldn’t find anything in SFOS. Changing the mobile network to 2G only gets me back to 4 days on a full battery.
With my X10iii the situation is similar (although i didn’t have it when 3G was still available): When connected to 4G (no active data connection, just idle/standby) it’s 2 or 3 days, when set to 2G only it’s 4 or 5 days.
So the if 4G is available and 3G isn’t that seems to trigger high battery use when connected to 4G. Does anyone else have the same situation?
My idea why this could be the case is because calls on 4G are special and one method to create a call is CSFB which falls back to 3G. So there might be some process in the baseband/modem constantly scanning for 3G while connected to 4G so it can change quickly when a call has to be made, since no network is found it keeps scanning and draining the battery.