There was no problem.
The gas tube is SUPPOSED to move in the receiver.
If it does not, then the key can cause it to wear out faster.
I go to a lot of trouble when assembling uppers to make sure the gas tube has room to move.
I also watch alignment up/down as MOST gas tubes can stand a little tweaking to make them ride straight into the gas key.
DPMS is really bad about gas tube alignment on 308's.
The ones I have seen used AR-15 gas tubes that had NOT been bent more like a proper AR-10 gas tube.
I put the extra bend into them when re-assembling and this makes the gas key align better.