Feedback when monitoring is on both channels

Anyway I tried recording a stereo acoustic tonight with a mic and di into my ur22mk2 and every time I turned the monitoring on through headphones on both there was massive feedback and crackling. If I turned one off it seemed ok but no sound was going through the other one. It seemed to be an either or situation. I tried it in logic as well and exactly the same thing happened. I have the latest drivers Mojave and Cubase pro 10. The funny thing is it was all working fine earlier in the day on a mixing project.

The other thing that was happening is if I had drums from groove agent and I pressed record on the di acoustic for some reason the drum track would record to it. Then I would get no sound at all from anything.

I’ve checked all my ins and outs and they seemed fine. I don’t know what to do and I have three more songs for an album I’m releasing next year to record. HELP!