[astronobob (Bob)]

Interesting capers Leo, after reading through comments my logic leans towards program capabilities, maybe try varying things, stacking only 50 images, or as David’s mention of alignment points, try a lot more or less of them if that is an option, some progs let you add one alignment point at a time for instance, , !
The moon is a big bright object and it can wobble at different frequencies across the surface, could cause further issues particularly if less favourable seeing conditions are used ?
Also try stacking in another program just to ascertain if is a program issu, could also do google or YouTube search ?

Just my basic Bob’s worth…