Thanks I followed your steps several times and the issue remained.
A workaround is in Settings, I set the "Default ICC profile if undetermined:" to "No default profile", so all the good!
FWIW for decades I've had it set to "sRGB" to show embedded JPEGs in raw files accurately, and this still works in Photo Mechanic 6 build R7212.
In Photo Mechanic 6, build 7269 it doesn't - unless you view at 100%. Deleting the cache between launches fixes it for a while.