Allright, thank you! Good to know that this is normal behaviour of the tool.
Still I get pretty awful result when stacking in Siril (both with or without Sirilic), not sure how to explain that. For comparison, I took a subset of my Auriga lights and stacked them both in Deepskystacker and Siril, underneath are the results after autostretch in siril and color calibration.
Stacking with deepskystacker:
Stacking with Siril:
I will try the multi image fit option.