Is the setting 'permanent' in the add_slot_iten action set to true?
Yes, i believe permanent true is the default option for this action.
How many slot item space does the squad have and how many weapons did it pick up before dropping models? Did every weapon require 1 slot space, or did some require 0 space? I noticed once that squads who have weapons which require 0 space tend to lose them.
I have the issue on various squad with difference setup, some have 1 slot but gain double weapon via upgrade. I use many slot item with 0 space but issue also happen on item with 1 space like SMGs. I will try change those item to 1 space.