when I tried to posses a giant it would do the fov effect on everything around me but I wouldn't posses the giant, instead it would lock me in the wandering state.

I only tried this because I have a mod that gives giants ai

does this happen if you try to possess a giant in vanilla too ?

It does not. I have tried it.

so, this is a mod compatibility issue right ? Which mod is it failing with ?

Closing this as missing the information required to fix.