I wonder if this is the cause for the UI failing and showing a white page with "server error". It has something to do with a failure to retrieve the site icon and if postgres is crashing that could explain why lemmy-ui is failing to retrieve the site icon.
My current "fix" for this is a script that runs every 10 minutes and sets the site image to NULL, curls the site URL, then sets the site image back to what it was. This does seem to work around the problem and if the UI does crash it's only down for a maximum of 10 minutes.