@abgestumpft The same as discussed in this topic perhaps In V5 processed images look different in V6?
PS:- It is very useful if as part of the post or part of your name, you include the platform you are using (Windows or Mac) because there can be differences between them and where a workaround might be possible that might vary between platforms, plus if another user wants to try to reproduce your problem it is useful to know on which platform the problem was encountered!
PPS:- and you might find PLv6: Color Rendering observations interesting.
Regards
Bryan