Green corners on Composure output

Have been compositing multiple green screen media sources with CG and always get green corners as per screengrab below - any ideas on why this happens?

I had this too for awhile, check in your chroma-key setup for “vignetting” values and adjust them so there isn’t any. Not sure why but sometimes the default is no vignetting and other times it has some which causes the green corners.

Thanks - changing the outer vignette solved it.