Glad you got sorted.
My own confession.
Recently installed the Cubase 9.5.40 update (which has a few issues it must be said) unfortunately I also updated a couple of other things at the same time. Suddenly my UR824 started losing sync after about 20 mins, I thought my UR driver problems where back and it was the Cubase update, turns out it was the latest version of Intel’s RST driver v16.7.0.1009… Uninstalled it, UR running sweet again. Which is more than I can say for the Cubase update.
Diagnosis courtesy of LatecyMon.