Rapid Maneuver can not be cast if looking directly at a NPC while the option "prevent attacking innocents" is enabled in the options menu.
This is odd, because Rapid Maneuver does not attack them and only buffs yourself and your party members. It's quite annoying in a town which is full of NPC's.
[minor edit for context]
Edited by ZOS_CoriJ on May 4, 2017 2:36AM