I just removed the internal flicker fixer just to see if it was that that was causing me drama...
It's not. With or without it, if I load up DCTV and click on the corner tab to switch back to my Work Bench screen, the Amiga will lock up. If I load up It's paint app, I am fine, I can click on the buttons below, but if I click in the drawing area, or try to switch to my Work Bench screen, the Amiga locks up once again.
Likewise, If I boot up with my SuperGen plugged in, the screen rolls kind of like displaying a PAL signl on an NTSC television.
I'm really starting to think I need to purchase an NTSC A600.
My 1200 is PAL too, but I'm going to set it up and run the same tests on it.
I think the problem lies in your choice of machines. The A600 has a newer video chipset and, I think, is the culprit.
I was a co-author of the DCTV manual. When we worked on DCTV, in 1990, the Amiga range stopped at the A3000. Since DCTV bangs the hardware quite a bit, I'm thinking you really need to be using an A2000 or A3000 with it. Also, the same problem might be occurring with your SuperGen....again, older video chips were used when this was designed.
Hope this helps!