Hi Lars,
I know of a SA user in Germany on 52nd latitude who also fiddled around with the wedge due to slippage problems. I could imagine this happens with a certain weight of the imaging gear PLUS the required latitude setting - Stockholm being on 59th, the problem would be even more pronounced?
Here are pictures of his adjustments (from 2015 - maybe the design changed at Skywatcher since then?), basically he glued a few teflon (!) pads to gain more tension where you did it with an extra plastic washer.
https://forum.astronomie.de/threads/...2#post-1182539
The 2nd image is about the illumination thingy, not related to tension in fixating the wedge. If you want to translate the post,
www.deepl.com/translate is a good choice.
I reckon your solution is the better one, looks more durable than several tiny pads.