power locks 99 Chevrolet Tahoe

I purchased a 1999 Tahoe , front locks would not work.  Dealership sent truck to private garage non dealership to fix.  He installed 2 front door actuators.  They went out within 2 days.  He did the same again and put a new relay in.  w-in a month same thing.  This has happened 7 times now.  I even got a new keyless installed aftermarket.  I am very disgusted,  I know the garage isn't taking advantage because he has not charged me for the locks and the labor each time except on the keyless, but he is getting frustrated he said that this has never happened before.  He said that he has tested everything.  The next step will be to rewire the locks.  Have you ever heard of this happening?  The motors smell hot when they go out.  Also I have came out to my truck am and it would not unlock to the problem occuring while driving.  Sometimes all of the locks engage and won't unlock at all.  I have to go to the garage or pry them up.