Also happens on Singleplayer.
Groups 1,2 and 7 (all other Groups were unused) got renumbered/changed:
1 to 7, 2 to 5 and all turrets from the former group 7 got unassigned.
edit:
This happened after jumping to another System
I only use turrets with independent targeting
/
Again, after loading into my SP-save -> All Antifighter-Turrets were set to 5, PD-turrets to 6 and all others to 7