I had 734 that went gunny sack last spring due to my shop being drenched when a tornado took part of the roof off of the shop. The remedy was to buy a 735 which is a real improvement over the 734 model. I'm not trying to be cute though it may sound like it, I am saying that if it comes to having to buy a new planer, you wure will be happy with the 735.
Wish I could help you with the problem that you have described, you might need to get it to a Dewalt Repair Center. Let us know what you finally find out and/do with the tool.
Jerry