Call URC again. We've run into the exact same situation on multiple MX990s recently. They told us to update our software and to try it again. They've definitely heard about it because we've called them 2X about this.

I think there is a bug in the remotes themselves as one of the remotes we sent back to them for the above problem was rejected. Once it got to them, they said "Oh...it works fine." They sent it back to us and the problem started 10 minutes later. We just sent it back to them with a video showing that it is defective.

These may be the Covid models (we've seen all sorts of QC issues not just with URC but with others) as we didn't start seeing MX990 problems until about 2 years ago.