Alternative to Dolphin Diagnostic - or anyone know how to repair them?

I have owned 2 Dolphin Diagnostics. The first worked very well for 5 years, then at the start of the next season it would turn off after about 1 or 2 minutes. I viewed the almost $200/year that it cost as well worth the savings in my time (an 18' by 55' pool with a deep end). The second worked for the first year, but now fails to climb walls, turn its direction, or stay on longer than about 5 minutes. A total waste of money.

I see from your web site that there are a lot of similar complaints so I am looking for advice on alternative products.

If anybody has had experience fixing their own, I'd like to hear about it (I have experience fixing a lot of electrical items - although many modern products have sealed components that simply have to be replaced). I am not willing to spend the money that the company would want to fix it since I would rather put that into a better product.

My theory is that the Dolphin's 3 motors are undersized for a very heavy machine. They all work the same: one motor for the drive belt, two for a split belt, one more for the vacuum function which holds it to the wall when it's climbing. I now have a Blue Diamond and its motors are about 3x the size of the Dolphin's.

You are most likely to have something clogged in the vacuum circuit or something jammed in the drive, which would cause it to shut down. I gather that all the robots use a change in the electric draw as the sensor that tells when it has hit an obstacle. If something's jamming it should tell the unit to shut down. Then again, the control unit could be shot. That's where all the brains are, as well as the receiver's antenna--the u-shaped handle in the power supply.