UR12 - gain problems, dropouts

Hello everyone. I am in big need of a help.
I recently bought the UR12 and cannot fix my problems.
I have MXL 770 plugged in to the interface and after I install and plug in the interface to the PC (Windows 10 Pro x64), my voice can be heard only in my left headphone, there are some dropouts, and not always the same level of gain received. (It is constantly doing some dropouts with a mix of gain differences)
Yes, the phantom power is on, I have reinstalled the Steinberg’s drivers, as well as, USB ports, BIOS updated, any other drivers for my motherboard etc etc. I have the 1909 version of Windows 10. I have used the LatencyMon before reinstalling any drivers and some of the drivers caused the problems. After updating the drivers I have none or some slight delays. The interface is in safe place (behind my monitor). I tried disabling my network adapter but still the problem occurs (after reboot ofc).

Is there any other advice or solution for my problems?

Thank you in advance

I will guess you are using a stereo input on the DAW, system or whatever software you are using.