Cutoff vs emissions

[Jon1967us]

I have a color tube on the tester that is showing extremely weak cutoff on all three guns, but good emissions on all three.

Is the cutoff the “first thing to go”? How is it possible to have almost non existent cutoff but good emissions?

The data is certainly backed up by image quality on screen which has lackluster contrast. Incidentally, the bias switch (on in this case a late 60s Sears Portable) has to be set at max for a decently viewable picture.