while driving on highway, electronics went berserk

We were driving on the highway in heavy rain and all of a sudden the car locks started going up and down, the electronics completely went out then back on several times. It went completely berserk. The danger though was that the engine upshifted to second or third gear and jerked the vehicle in heavy traffic while moving at around 55 MPH. Then I could not get the engine to accelerate.

I eventually was able to pull over and shut the car off. We were in a very remote location so before calling for a tow, I tried starting the car again and she started right up. I drove it the remaining 200 miles home without incident. Since then I have had other very minor incidents but nothing like that. I have taken it to the Cadillac dealer twice now. The first time they told me that there was an anomaly in the electronics but they had no additional info and could not do anything about it.

The car drove for the rest f the summer, just fine and then one night the blower for the AC just quit running. I dropped it off at the dealer again today and they confirmed that the blower is fine but there is an electrical problem. No duh. I googled the issue and came across this other fella who described the exact scenario that we experienced and said that replacing the negative battery terminal was possibly the fix and was unclear as to whether another permanent fix was available.