There are two possible ways to read this:
Robots may not intentionally ((detach parts during any Match), OR (leave mechanisms on the field))
Robots may not (intentionally detach parts during any Match), OR (leave mechanisms on the field)
Is the “intentionally” part of the rule supposed to apply to both “mechanisms” and “parts”?
Yes. It is expected that parts will accidentally detach from time to time. (e.g. Teams regularly lose nuts and bolts during a match. It would be ridiculous to penalize them for this.)