[old_tv_nut]

If the yoke is out of position, it will mess up the purity, in general around the edges more than the center, which looks like what you have.

If the degaussing is not working, it will affect the purity after the set is moved. It could be corrected with a manual degaussing pass, but will recur when the set is moved.

The two basically do not interact - but both need to be right.

A hard drop that distorts the shadow mask will be uncorrectable - hope that's not the case here.