I keep having this issue where my NPC henchmen, namely the Castle Gloom follower NPCs decide to attack me when combat starts, or when combat ends at random intervals. It's incredibly annoying, considering they crit for upwards of 90, while I'm a mage with ~130 hp. Two hits, and I've just wasted a load of experience and have to wait on the stat decrease. This adds up when it happens regularly. Incredulously frustrating.
edit; Here is my combat log to portray that I haven't cast anything that would turn them hostile.
Another possibility is the slow spell. I don't actually know how it interacts with henchmen or summons because I avoid casting it near friendly NPCs. I do know that if you catch a dominated NPC in the effect of a slow spell it ends the domination even tho they do not make rolls against the spell because they are not hostile when it hits.
Perhaps a spell that only affects hostiles is registering as an attack even tho its not affecting them.