Error: AQL: internal error -- in index

When any error containing Error: AQL: internal error - in index is shown after any main action after upgrade (for example after Unloading snapshot or starting Network discovery).

The database got corrupted (no worries all of your data are safely stored) and is necessary to run maintenance.

This can be done in Settings → Advanced → System in the main GUI. For more information see Schedule System Maintenance.

If this does not help, we recommend restarting ArangoDB process in System Administration (port 8443) System Status and running maintenance -- see the previous step.