Monsters not attacking
Some people have brought up the issue relating it to different abilities (mostly the shadow/stealth stuff) but a lot of the bigger monsters seem to have a hard time targeting the hit-box and will often just stand there and look at you menacingly hopping you will go away. They will continue to cast spells when they can, but unless their spell displaces them or you they will stand perfectly still.
Monsters sometimes stops attacking, i experienced this behaviour in fights here and there.
One possible relation i want to add, probably the skill Relocate also cause the non attacking behaviour.
It seemed that it often happened when i used Relocate right before.