These new ones have a totally different controller, or you can use an apex and I believe some other controllers are compatible? (not sure on others) But sounds like you were taking it a part a lot for cleaning.. my 40B i've never taken it apart to clean and it's been rock solid.. the one on the 75 I took apart about 4 times.. got it in April or May of 2015 I believe. I noticed the end covers bowing out and realized it was from the way I was taking it apart, the best way to take it apart is don't pull on the end cap, pull on the shaft where it connects to the motor.
I think these things aren't highly durable when it comes to disassembling/reassembling (or at least the 100 series) so care is needed.. I'm gentle with things so I probably have had better luck than others.