3rd gen 4.88 and ARB lockers with a clunk when shifting (auto)

As the title says,

I just had a shop do my gears and lockers and now I feel a slight clunk and hard shift into gear (up and down) and when I let off the gas and then tap the gas again (think stop and go traffic)

My question is, and forgive me if my assumption is stupid but, doesnt that sound like the backlash was done incorrectly? Like there is too much play in my shaft and it can be a pretty hard shift.

The prob is gone in 4wd. Drives and shifts like normal.

The guy who installed them has great reviews and does tons of jeep difs and I dont think hes an idiot or anything but maybe he rushed the job? I called him and he seems to think that the spider gears in the Locker are prob a little sloppy. I called ARB and they said that if I lock the gear and the prob goes away its the spider gears and if not its another problem. I locked just the rear and it seems to help but still a little bit of a hard shift. I got under and everything looks good, nothing visually wrong or anything that would stick out.

Any ideas?