In the Acquire menu, I like to use the averages mode for getting much cleaner looking signals, like now I was on 50 or 20ms, looking at 4ch's. And when when I changed the time base to 20 or 10ms, no signal was being show on screen, so after a few moments still nothing o screen at all, so go back to back to normal acquisition mode, and I get this, changing every few seconds, mostly the displaying the noisy image, (which it does look like, that's why I used average mode, it's a small noisy signals from my DMM I'm working on).
I have hacked my scope to 1204, and with latest firmware, it says it's still 1204, so IDK if that's an issue.
the last image is more or less what average mode looked like
This happened a few times, where I had this scope start just showing points, either when changing time base on average aqq. mode, and/or when I went back to normal aqq. mode, I can't remember.