It has Gotoh Magnum locking. New strings. Maybe the strings are catching, he did a full set up and he works for some pretty big bands as a tech so i doubt its the set up, but everyine has off days. I was thinking it was the tuners cause the just seem like they arent holding the string...
If it's catching at the nut, you could lube it. I use Dr. Ducks Ax Wax for many things including that, but many people use graphite on the nut. Good luck.
You could restring the guitar and wrap the strings as if the tuners were standard tuners, if this works and the guitar stays in tune then I would say its locking mechanics on the tuners are bad.
overtightening the locking on tuners can ruin the mechanics that lock the strings, I don't belive this can be fixed, but a new set of gotoh magnum locking tuners would be around $70.
I would make shure its not catching at the nut first.