I GOT IT!!
I was using the auto patch feature so I was confident of the addressing.
I didn't realize there was a pre program for the DP-DMX20L. I was using the generic 4ch program and the dimmers didn't like that.
Changed the program and put the scan's last in the chain and PRESTO, we now have stability.
I also moved the scanners addresses further away from the dimmers.
Thanks for all the suggestions. Hopefully I can return the favor someday.