Resource Reservations being deleted every 20 mintues

In our Resource Reservations database the reservations are being deleted after the reservation time has passed. There is something running every 20 minutes or so deleting past reservations. We want to change this so we keep more history in the database. The Purge Documents agent is NOT running, it is disabled and there are no other scheduled agents in the database. There are no archive settings enabled. If I make a copy of the database on the same server those reservations are not deleted. What’s deleting them? Is there a server task that does this? All other posts just talk about the Purge Documents agent.