@deckingman:
A lot of people are falling into this trap - you need to read the release notes. To save you time, the release notes will tell you that unless you need to deploy and retract a probe, you need to delete any deploy probe and retract probe files that you have in you .sys directory.
Nice idea but I have no probe nor any probe files in sys.
But:
Important! On a CoreXY machine, if upgrading from a version prior to 1.19beta9, you need to reverse the Y motor direction in the M569 command. Similarly for CoreXYU machines.
I missed it because it it so obvious that an axis will have to be turned around after an firmware upgrade.
Will try after my Print is finished.