Well I took a little trip to the Watcher's Keep (I'm still low leveled but I wanted to get the Firetooth crossbow) and I'm having some really strange reactions from those false Helm guardians. As soon as I enter their visual range they target my protagonist with Hold Spells (?). They are still neutral after that and I can talk to them normally and start the quest once the hold wears off (or I save vs spell). So I talk to them, get transported up the stairway and then they do it again, again Hold spell on my PC. Any idea why?

Yes, it's a bug. Thanks for reporting it. I'll fix it for the next release. But I also send a quick fix here.

1- Uninstall the mod
2- Download the attached file and put it into "scripts" folder (the "scripts" folder is inside "ImprovedAnvil" folder in your main BG2 folder)
3- Install the mod again.

Let me know if it's fully fixed.

Yeah it's fully fixed now

Glad to hear that it's fixed.

I should emphasize that the bug was not the fault of IA testers; it was my own fault as it was the result of some quick changes I had applied to that script minutes before releasing the mod.

Of course, even with that bug in your game nothing serious would happen; the knights would cast some Hold Person spells, but everything would proceed normally afterwards.