We confirmed the problem, it was with a another change that was made in 20.2.2 to avoid crashes with DSCP. What will happen is once there is a free entry in the NAT table, later entries are never having their timeout decremented. Once the NAT table is 100% full, all the timeouts will start decrementing again. You will see a periodic graph of increasing NAT entries, then decrementing, then incrementing till full again, etc.
If you have NAT SMs you should not run 20.2.2. We will fix this ASAP.
If you have a MicroPoP Connectorized AP you need to run 20.2.2. Everything else should stay on 20.2.1.
Thanks to @MW_WISP for finding and reporting this so quickly.