Chroma Screen intermittent black area

I have Manycame set up with a virtual background and it works well with replace and auto
However, after some random amount of time, a black area appears behind me of varying size that moves and looks like a black cape fluttering away from my neck
It eventually returns to normal and I can sometimes speed this up just by going to the Manycam app on my desktop although not always
So I set up my green screen added some lighting and changed to chroma key and color picker thinking it would solve this problem
It did not and the same aberrant behavior occurs at random points in time
I have messed with the variations on settings YUV vs HSL and Spill and smoothness but not having much luck
Apprecaite any suggestions