it' looks like one of 16-k banks is broken (4 or 6). Run a diagnostic test )
Diagnostics said that all is ok. It was one of the first things that I did after I bought the Dandanator.
I did it again with the same result as you can see in the image
How is a speccy connected to TV-Monitor?
I can confirm that the same issue happens on MiSTer when 128k is using 48k video timings
I am using a RGB cable
(sorry for the late answer. I past all the day in another city)
