I think you are correct. There is some software that is making this battery hardware issue less forgiving and make the system restart.

I resetted my Jolla when 1.0.7 came out. I was using the white OH until 3 days ago. I never had a reboot issue since I resetted. As soon as I installed The First One ambience, it started the reboot issue. It was really unusable. I put the white one back and it continued to do that. I removed the first one ambiance but did not solve it. But I added my paper patch and it stopped.

It is possible that it was just in a good position before I inserted the first one OH, but it is unlikely because I did not take the battery out.

I also have the issue of network error noise after an incoming call ring ends without picking up, that is so annoying. After resetting this did not happen until I enabled some default Ambience, I don't remember which one. I removed all ambience, but that noise does not go away.