UR22 mk11 and high pitch squealing noises.

I bought the ur22 mk11 in May and it worked great at first. I have all the updated drivers and firmware that is required.
lately when I’m using my daw (mixcraft 7) I get a high pitch squealing noise similar to feed back but different. This occurs when I have my guitar plugged in and an instrument track armed in my daw. If I play straight through it does not happen. just when I have a vst selected such as guitar rig or something simular and when I press the monitor incoming audio button to on. I have tried everything I know to fix this, different cables, reinstalling my software checking all my inputs and out puts ect.
Any help would be appreciated as I have wasted many hours and days trying to solve this issue.
Thanks Alison