Patch tool not patching

I freelance at various locations as a retoucher, and I notice that on some workstations the patch tool doesn't work correctly. When patching dark areas it just creates a dark blob of the area. Yet if I go to a different workstation, even in the same work location, I can properly patch the same area on the same image. This happens with Macs and PCs, and even different versions of Photoshop.

I look at the settings for the patch tool, and there essentially aren't any. I have no clue why this happens. Has anyone here ever experienced this? If so are you aware of any settings anywhere that can correct it? Thanks for any info on this.