Originally Posted by
lnanek
if they didn't put loctite on the bolts, didn't put carbon grip paste on the steerer, and didn't make sure any expander plug in there is under the stem bolts. .
These are classic issues. Have you taken the bike apart yourself to check if it was assembled correctly? I had a similar situation with my daughter's bike; it was loose and wobbly. The person who assembled the bike hadn't used carbon paste and had cut the steerer tube too long. I ended up disassembling it and spent a couple of hours rebuilding it properly.