MangoGT unit that had previously run out of memory (see MangoGT running out of memory? restarted, but the UI failed to present a login page. After several attempts, I moved the databases directory and recovered from a recent backup. I have tried this several times now, going further back in the backup history, but with no success.
Then I noticed a very unexpected behavior: one browser window which was logged in to do the SQL restore DID let me log in, somehow, and I am able to operate normally in that browser, for now. However, other browsers just hang on a /ui/ URL; or if I access the device using a different URL (e.g. IP address) it hangs similarly.
I am sending the URL separately so you can try for yourselves, see the HTTP conversation.