I gotta agree with you Joe about squeezing through and not being able to turn around. Anyone ever been in a cave, crawlspace, or attic area that is too narrow to turn around in? I have an attic area is not very navigable.
You could always Rule Zero it and say, if the monster is squeezing through an area, to give it facing and it cannot turn around.
With all the cramped adventure maps, the instance of this might be too often though (if you run the adventures as written). Half the time though, I'm like, "This room is wayyyy too small. WALA! It's now 10' bigger each side..."