Retro computers and "jail bars" on the screen
Those 'jail-bars' appear to be a synchronous subset of the horizontal trace. They are very clean and well defined. Suggest tracking down horizontal circuits and replacing the electrolytics in just that section.

If problem still exist try to find a point where you can modify just the vertical bars and nothing else.

At some point you may stumble into a leaky transistor or bad IC. Bad resistors and capacitors tend to open up and loose value, so check those in the horizontal section.