Fixing a miniature CRT (viewfinder)

So, I got this miniature CRT from the viewfinder of a old panasonic CRT camera.
Knowing very little of electronics I figured out how to connect 9V, video input and ground.
The problem is that external video looks stretched down, vertically…
I’d like to take this as a project for learning how b&w tv works, learning how to use a multimeter and hopefully make a wobbulator out of this… So I’m hoping somebody here could point out what should I check to make this work.
I took this to my local old school technician and he told me there was no fix for it, but I’m guessing he just wasnt in the mood for fixing it as he basically refused to take a closer look at it.
Any insights will be appreciated. Thankyou!
I can take pictures of the PCBs later on.