This was probably one of the nastier 20EZs I've worked on. I don't know what this thing's past life was but it was pretty rusty and coated in dirt.
Regardless of how dirty it was, it will clean up fine. The problem is that the picture was screwed up. It was dim in and had partial vertical collapse. You can even see some waving.
One thing that is super common on 20EZs is that the electrolytic capacitors go bad. This is especially common with the higher voltage (160V) capacitors. Typically the burst on the bottom like these. When they go bad they can cause brightness and deflection issues in my experience. Just replacing the capacitors will fix a lot of these issues.
After a good wash and a recap, the monitor was back to working like it uses to back in the day. Lots of times with these it just needs new capacitors.