Oscilloscope Gould OS300 horizontal trace problem

[jpwm]

Hi,

I recently purchased this oscilloscope on Ebay, unfortunately the seller packed it badly so that some plastic parts of the case broke and the CRT came loose. I pulled it back into position and fastened it with cable ties. Unfortunately the horizontal axis doesn't work properly anymore.
The trace of both channels can only be moved horizontally in an area between the left edge and the middle. Both traces can be moved vertically over the complete height up to outside the CRT.
I have the manual for the oscilloscope, but so far I have only worked with considerably newer devices and therefore I can't really understand which setting could solve this problem. Online I found some similar questions, but there were never satisfactory answers. I would be happy if anyone had an idea what the problem is.

(I also uploaded a video of the problem: https://streamable.com/z8c7c)