Looking into lnd’s log file, I found that the lnd service was restarting every 1 minute. The lnd wallet was actually being unlocked for about 2 or 3 seconds, then locked again for about 57 seconds until next restart. This cycle was repeating forever.
After some experiments, I also found that the cause of this ‘lnd restart loop’ was that there was a Tor connection problem.
Execute
ls -alt ~/umbrel/lnd
If you see a file named ‘v3_onion_private_key’ with a size of 0 bytes, then you need to delete it.
In my case, it started to work fine after deleting the file.
Just as a reference, here is a part of my lnd log. https://pastebin.com/E6ZsKTpu