I've had this happen also.
Logged back into the game the other day near to Old Six-arms spawn, next to some friends who were killing the fat dodos there for fun- a green icon was next to the mob name but not others (as I have it turned off). I was not in active mode at the time.
Then doing 30 leves in nanawa mines yesterday, one of the Puks in the local area near some Necrologos spires had the green "aggro" icon next to its name but not the others. I was in active mode that time.
I get it randomly happen on and off- think it has occurred 3 or 4 times now.