RE: Airfield 800mm P51 rtr.. Tail is crooked / spinner wobbles / return?
You would have to talk or PM someone at Nitro about an exchange.
Unless the shaft is actually bent, it may not be worth the effort. Fixing misalignments in foam parts is quite easy, requiring only a few minutes work and a bit of glue...
White glue works pretty well, leaving the original finish looking good.
The key is to get a good initial cut using something thin. I've started cuts with hobby knives and continued with fine hacksaw blades.
However check the shaft first... as this will determine what you should do.
BTW: unless the tail is so far out of alignment that it looks horrible, small errors in angle will barely affect the plane if at all.