Very long story short I was forced to upgrade Seafile from v6.xx server install v11 docker install. This didn’t work (upgrade failed somehow) and after vanilla install for debugging, it crashes my raspberry pi 3 (first becomes very slow and then entirely nonresponsive, cannot even SSH anymore). I tried multiple times but every time I start the docker container (or re-compose it), my entire device crashes.
What the hell? What can I do to even start debugging this? 
FYI I took care to stop the initial container (from the upgrade) first.