Hello Shawn,
A pilot in my area had the same thing happen running a similar setup. He was not using my regulators and the ones he had were too small to be used alone. He got about 5-6 flight and then noticed that the plane got sluggish and then shortly there after he lost complete control. He came to the same conclusion that the dominant regulator heated up, failed or shut down and then the other regulator took over but could not handle the full load and that was that. I would ask if your plane got sluggish first and then completely lost it. Anyway, if you use the BatShare you need to make sure the regulator you have can handle the full load. Another option is our SuperReg which has a BatShare built in with a 7.5 amp regulator and a failsafe switch and was buit to be a companion to our PowerExpander. Its terrible to loose a plane (unless you are lucky enough for a full ride and don't care) and there is no way to guarantee 100% redundancy but if your regulator is big enough to handle the load (and this means good heat dissipation, not just a 10 amp rating) then the two most common failures are the batteries and switches (or associated wiring) with regulator and receiver failure way, way behind these. This is why we built the SuperReg and TurboReg, regulators that can handle the load required and provice battery backup and failsafe switch protection.
Please let me know if I can be of any further assistance.