Bearings were replaced when all the other work was done

 

My guess is you speed sensors (black wire going to the wheel bearings, need an Allen wrench to get it off). I suggest pulling them out and looking in the bearing for rust, and also look at the end for any possible foreign objects or rust on it. Also check the spacer, make sure there is one and only one on each. I changed the bearings on a friends blazer and accidentally put the new and old spacer on and had the "skipping" issue. Took a spacer off and it was perfect. And also check the wires and see of they are pinched. That's my best guess.