Here's the reasons why I think a submissive may break rules set by a Dom.

1) The orders where too unclear.
2) It was unpractical to follow the orders at that time.
3) It's a bad rule which makes the subs life too difficult.

I'd say the top two are unavoidable and the third one has to do with how well the Master knows his slave. If a slave keeps breaking a rule then it may be better revising the rule than to keep dealing out punishment. And if the rule is important for the Dom then, well...some people just aren't meant for one another.