The topic is a year old and ...
Oh, my bad, I've completely overseen it that the thread was necro bumped.
i found my problem. it was the sd card, the card was very old and umbrel tell me at one point i should change it.
This "new" feature of Umbrel was in many cases more of a false alarm and quite a gimmick to be honest. But it doesn't hurt to use quality microSD cards in a Raspi. I use mostly Samsung Endurance variants which can withstand quite some write load and so far I hadn't a single one failing in my Raspis.