I wouldn't be happy with that and would send that picture and accompanying text to Stag CS. It's certainly a sign that the assembler didn't bring his A-game to your rifle. Your rail attaches to the barrel nut, right - a free float? Can be a simple fix if you have the right tools.
The biggest issue with assembling an AR isn't so much getting the parts together right - it's getting the right parts together.
US Army 1966-69, VFW Life Member, Retired Geek