While accessing Special:Watchlist in Wikimedia Commons I often get an error like:
Database error A database query error has occurred. This may indicate a bug in the software.[WcASvgpAMFcAAHnenmMAAAAE] 2017-09-18 18:39:54: Fatal exception of type "Wikimedia\Rdbms\DBQueryError"
However, this behaviour seems to be a bit random (sometimes the page works)
The problem was also reported by another user (User:Electron) on my talk page who also reports that regardless the page loads or fails the page loading time is long (20-30s).