Tablet: UI broken after update; can I fix it without reset? [not relevant]
EDIT: Thanks for all your advice. Unfortunately, while trying some of the things described below, my device ended up in a state when it wouldn't boot past the Jolla logo. So in the end I had no other choice than reset via recovery mode. It was the first time I had to do this with a Jolla device since I bought my first Jolla phone in 2013. :)
2.2.1.18 killed my tablet. It starts up and I get a screen that looks good, but once I swipe away the lock screen, all I see is the background image and a spinning indicator. I can not access the app drawer or the events view.
The only thing that works is: I can ssh into the device and become root. First I tried to re-install 2.2.1.18 manually (version --dup). That seems to have done something: At least when I ssh into it now it identifies itself as 2.2.1.18, which it didn't after the first update attempt. Still, the UI is basically dead, no change here.
I'm aware that healthy and sane people would probably just reset the whole thing, but I'm not a mentally healthy person. I'd like to find out what caused the issue, repair it and live my life happily with 2.2.1.18.
So my question is:
What is most likely causing this? (Lipstick maybe?) Are there any log files or debug modes I could use to solve the problem? In which order should I examine various parts of the system to check if they are OK?