I tested it again in the current patch, there is no such bug for me. Also, only 2 of all the monks are enforcers (they wear gray clothes instead of black and have a cane at their belt), so if you are not near them and they don't directly see you, you can afford to have the "neglecting your duties" warning for a while without them catching you.
If you don't want to do this quest as a monk, you can simply let yourself being expelled from the monastery (do something bad, then instead of letting them arrest you, resist and they will throw you out), pick up your stuff, wait until night, preferably drink a saviour schnapps to be safe, use lockpicking to break into the monastery (lockpicking around 10 should be enough, not sure if less works, you can also buy a Padfoot potion from a herb woman to buff your lockpicking by +5), then sneak into the dormitory, knock out the right novice (if you don't know it yet, google which novice is Pious, I don't want to spoil it here), you can either kill him right at the spot (probably monks will wake up and soldiers will come quickly, you can simply run away through the door you unlocked) or you can try to grab the unconscious body and kill him somewhere without waking up monks and simply walk away). That's the easy, violent solution, it completes the quest.
If you want to do this quest as a monk or if you are trying to get as many achievements as possible, then you have to look up some guides about this quest, there are both written and video guides about this.
