When I spoke with thefoo.83 about my cable he told me that he is now putting 470 ohm and a 220uF cap on the sync line. I also don’t think the 220uF should be there. So I don’t think spritti made a mistake, the SCART head should be empty otherwise (ok, maybe one more resistor).
My cable did not have the 470 ohm resistor but the picture with the OSSC was looking just fine. I added the 470 ohm resistor into the SCART head and did a quick test with my ‘lab’ TV and got a rolling picture. Hm, weird. Maybe I messed something up when removing the hot glue from the stripper box. I accidentally disconnected the sync line from the LM1881 input through the cap, but soldered it back in place, did continuity checks and everything that ought to be / not to be connected was correct. I didn’t want to mess much more with it since I didn’t want to risk to continue using a cable that was wrong and I didn’t understand 100%, very happy with my RGC csync cable now. But still, would’ve loved to understand the issue, just for my own education.