[CA] [CA11] C120 video has fast horizontal shifting

[CaptNorm]

My C120 plotter has worked perfectly for many years. On my last cruise, it worked great for about an hour then everything started shifting, very quickly, horizontally a very small amount. Initially, I was able to still read the text. After roughly an other hour or so, the shifting moved the text more and more. Roughly an hour later the shifting was so bad, the whole screen was unreadable.

I had the diesel on, so turned it off to run strictly from fully charged batteries (thinking there could be some alternating current noise). I turned everything possible off (thinking some RF caused this). Even after turning the C 120 off then back on, the shifting came back

Is there anything else I can try (it can be reproduced after roughly 30 minutes)?

Can a graphics board be swapped inside the unit? Does RM have any of these in stock, what is the cost?

Thanks