It is important whether the bottom bracket bearing has an adjustable (non-drive side) cup and lockring, or whether it is of cartridge type.

Based on what you've said, this sounds like the older-style adjustable type. If it has caged bearings within the two cups, you might want to uncage the bearings and re-install. This method has solved a similar problem for me over the years. Also, the shop may have inverted the cages, which would be a sad thing to discover.

Proper torque to the lockring is important, too.

If you have the cartridge type, I'm at a loss to advise you.