I have been running an Umbrel on a Raspberry Pi too, and it acts unstable at random moments like yours. I have seen others saying those problems stop if you choose someone stronger to run it in.
Discussion
Yeah, nostr:npub1aeh2zw4elewy5682lxc6xnlqzjnxksq303gwu2npfaxd49vmde6qcq4nwx is reporting this as well.
If I could do it over, I would have just started on a standalone PC with a better processor and more RAM.
Makes sense, I eventually got frustrated and turned my old thinkpad into a start 9 node. My only complaint is that Start 9 doesn’t have Tailscale or WireGuard yet.