Whoever installed those spacers should hang up his wrenches and go work at Dunkin' Donuts.

Using spacers on a GXP bottom bracket may seem to solve a clearance issue but - because the spindle attached to the drive side crank arm doesn't magically grow when you add spacers - it also means you need to over-tighten the non-drive side crank arm bolt to get the crank arm to fully seat on the spindle, which in turn crushes the bearings.

Essentially, your "mechanic" ruined your bottom bracket. Go back to the shop and kick him in the nuts.