Tried playing mission 6 and I would get minute long freezes occasionally. I'm about to try again after a restart to make sure it's not my issue, but it may have to do with the recent looping trigger changes Blizz made to the editor.
EDIT: Keeps happening. I'm unable to play the map, is this happening to anyone else?
EDIT EDIT: It seems to be linked to me damaging/destroying the enemy cannons. Once I eliminated all three, I encountered no other freezes.