Tmtomh's on the right track. I think that you will find that it's just a flaky solder joint or poor connector. Your problem of insufficient width means that the horizontal deflection is weak. However, that circuit is intimately coupled with the high-voltage circuitry. The fact that the focus is reasonably good (at least as far as I could tell from the pic), and that the height is more or less correct, indicates that your HV circuitry is ok. That, in turn, implies that the basic horizontal deflection circuits are probably ok, too. That leaves a bad connection as the most likely possibility. There are others, too, but don't worry about that just yet.