The vast majority of "mechanics" in shops do not truly understand wheels or how to fix them. The wheel was poorly tensioned initially. Not surprising as most machine made prebuilts are.

You shop never re-tensioned the wheel - they simply tightened the loosened nipple and trued the wheel. That will never fix the problem.

The vast majority of shops don't have tensionmeters. If they do they either don't know how to use them or use them incorrectly. Even the "top wrench" is usually someone who learned from an old gray hair back on 32 or 36 hole wheels and crappy single walled rims where the tensions were so low you practically couldn't go wrong. Lower spoke counts and way higher tensions and stiffer rim profiles mean that the wheel assembly can store a lot of imbalance when assembled. If you don't completely alleviate that while tensioning and building then you're bound for failure.

So - no...your shop never "fixed" it. It's a poorly built wheel. In the hands of someone who actually knows what they are doing odds are it can be repaired correctly to the point of never having to worry about it until one of the sub-par quality components fails through normal fatigue...but apparently your shop doesn't have anyone good enough so you are stuck with the routine the rest of these guys have to deal with:

1. Learn and do it yourself (I have found that there really aren't many who can do this well without some direct guidance).
2. Send it to someone who does know what they are doing.
3. Have them warranty the wheel and get you a new POS out of the box machine built wheel that you can ride for a while until that one has a problem then do the whole thing again.