1996 Chevy S-10 Gear Shift Problem

1996 Chevy S10 Regular Cab with 4.3 L V6 and 5 speed manual transmission. The truck has 78,000 miles and I just had the clutch, flywheel, clutch bearings and slave cylinder replaced. My question has to do with the manual gear shifter. Before it used to stay centered on 3rd and 4th gear when in neutral but after the clutch repair it just slops back and forth. I can’t seem to find a detailed schematic to see if a return spring was left off or what the problem might be. The mechanic said this was “normal” and didn’t see a problem. Any ideas on what could be causing this? Thanks for the assistance.