Probably had a little bit of the manufacturing oil coating on the steel left over. This would prevent the paint from bonding. Whoever at Lang prepped it for paint did not hit that spot well with solvent wipe down to get any residual coating off.
Short of shipping it back, you are going to have to address it locally. A little wire brushing, light sanding to blend the edges of the paint and high temp paint to match should fix it. I would contact them and also document with an email. If I were Lang, I would foot the bill for a local shop to do the work instead of putting that burden on you since it's too far to return the smoker to them. If it continues in other areas, then you have a more serious problem and they should pick up the tab for shipping it back and swapping out. It's probably an isolated incident, but document just in case. Lang will likely make good on this.