Here is a "maybe".But I sure could be wrong.
I'm guessing the gun is all stainless.I'm also guessing (I do not know)that DW heat treats the steel to approx. the same hardness on the frame and slide.
AFAIK,DW fits everything to very tight clearances.
You said you degreased/regreased it.I'm guessing,you maybe used a chlorinated hydrocarbon such as Brake or Carb cleaner?
A number of factors here add up to the possibility the slide/frame ways may have galled.
And,that is not necessarily DW's fault.
I used to build steel molds that had closely fitted parts which had to run many cycles under loads.Galling could be a problem.We had ways to avoid it.
Some stainless steels are prone to galling.
Tight clearances are prone to galling
Working parts of the same material are more prone to galling
Working parts of the same hardness are more prone to galling.(Hint,we used a guideline of 7 points Rockwell "C" differential)
The orientation of the "lay" of surface finish plays a roll.Best to grind surface diagonal to direction of travel.,or even leave mill cutter marks that transverse direction of travel.
Worst,both parts have a lay in the direction of travel.Such as,when tightly fitted slides are lapped.
The stainless may be a sulphurized steel.Chlorinated hydrocarbons are a bad idea on these.The solvent actually attacks the sulphur within the steel.See Schuemann Barrels website,advice on cleaning.
Some lubes are better than others for stainless.
The recoil spring has a closed end and an open end.Is the open end inside the plug?
It might be your degrease/regrease did not work out so well.
Also,any sort of guide rod or buffer things going on?