Whatever it is, it's -nothing- to do with the mods to stat-checking. The system that takes your stat, rolls some virtual dice and calculates a result was editted, this code doesn't -ever- touch your stats except to read them.
That said, there are several IC acts that effect various stats. It's the way it's coded. We won't now, or ever, reveal details of how various coded things work but I will offer a couple of hints. Your stats go up with experience (UE) but that isn't the full extent of how stats change. Drugs can effect your stats, eventually alcohol will effect your stats, cyberwear will effect your stats and so will a variety of other things. Stats going down is -not- unusual.
Regarding charisma… why might charisma go down? Charisma reflects your characters appearance, social abilities and personality. Things that make your character less appealing will effect your charisma. Doing things that aren't socially acceptable -could- effect your charisma... Any of the following already, may in the future or theoretically could effect charisma: Killing people, not bathing, wandering around in sewers, performing unsavoury acts on corpses, carrying weapons and any of a million other things.
Spontaneous reduction of stats does -not- happen.
