Audio error on UR824

Hello anyone can help me with my UR 824?? suddenly my UR sounds out the high frequency noise (similar to feedback) while I change audio setting on wavelab’s preferences. every input I used (no.2-8) became overload. but if I opened up cubase the noise would dissapear and back alive every I close the cubase. But the above conditions just happen if line out routing on DSP mix set to “mix L/R” and when every ouput level going high above -20db.
I’ve had trying to reinstall the UR tools and reupdate the firmware but the problem still exist.

anyone can suggest me how to solve this problem?