I have noticed that while running in Cyrodil that any time I try and cast restraining prison while on the move against other players I sometimes get the animation and sometimes do not which in turn equates to about a 90% failure rate of casting it and having it hit against enemy players. Guards I have no problem with the skill although I do not always see the animation, but against players I actually have to stop and cast which is inconvenient as all get out while running with our 12 man.