Hi Jeff
Unfortunately it's not just the one particular query, there's no pattern that I can see besides the time they're being executed.
We did go from Autovac only to nightly vac. I'm going to implement autovac again, we've been operating without for a few months now. Will run both nightly manual and autovac to see how things go. On a side not, we're not doing a vacuumdb, but individual vacuum analyze statements on each table. Not sure if that makes any difference.