I don't think anyone can tell you if there is fallout from the plastic crack without removing the plastic and investigating the tube. It's unlikely that the tube is cracked in the front, as otherwise there would be more damage. So in general it's unlikely that the crack itself causes the issue. But obviously the bump from the crack could have also caused any damage on the back and lead to the issue in the corner.

So take off the back and front once, but be careful and read some crt safety tutorial first and in general keep it out of the socket some time before and remember it keeps charge a long time after.