Poor quality control. The back panel  on mine had holes for the lock tabs that were only drilled to 1/2 the proper depth. I spent an hour with a Dremel getting the holes just the right depth but 90% of people never would have been able to do this. Once these packages are opened it’s nearly impossible to imagine sending it back. Could have called for a replacement part or refund I guess but how many more hours would that take? Once it was together it’s a decent mid quality bench.