Red focus

[lnx64]

Eh, I just noticed something that I've never seen before and don't know how it's possible.

The red gun on my Samsung is a little out of focus.. Not much, I can still see scanlines but not as refined on an all red screen.. But blue and green are crisp and sharp..

I can focus red to be very sharp via the flyback, but then blue and green loose focus just like red..

Would this be a deformed shadowmask?