I have a Daniel Defense 9.0 on a mid length build.  The rail leaned to the right a bit.  Looking at the muzzle end of the handguard, the gas tube was very close to the rail on the left side of the channel (assebled correctly BTW).  I tried not to let this bother me since I'm still using a standard front sight gas block for now.  

I plan on changing the barrel configuration in the future and mounting a sight on the rail.  The offset rail started to bother me so I contact Daniel Defense about it.

I contacted them and offered to send it back for evaluation.  DD returned my email with an offer to send out a new one with a UPS tag so I could send in the old one for evaluation.  They already knew why my rail was slightly off and were eager to make it right.

The UPS guy was at my door before I had even removed the old handguard.  The new rail arrived the following day (day 4 after initial email).

The new handguard mounted up dead straight.  I opted to use my existing barrel nut and just mounted the new rail.  Considering tolerances in upper receivers, I'm very impressed with how well it mates up.  Problem solved.

Excellent customer service.

Glad to hear they made it right for you.  DD puts out some good stuff.