Next time - review everything before doing any mods
Having assembled a sh-it pot ful of ARFS and BARFS - I agree there ar errors in some and if I were to just sit back and send problem pieces back to th seller - I would still be assembling ones from years back.
The wing tube -- NEVER sand the tube - sand the socket it goes into.
wrap stick sandpaper say - 220 grit around a slightly smaller tube/pipe/stick - and turn it slowly in and out of the socket --always moving it in one rotation such that the sandpaper does not bunch up- remove and dust often - I have fixed a bunch of them this way .
Take some soft balsa and using a piece of brass tubing - plunge into the end grain and make some plugs which you can glue in with Gorilla Glue - - insert these in hinge locations and install (when dry and sanded ) the new hinges . Dun this one too fixing screwed up hinge alignment
these tricks are far faster to do then ship sh-it back n forth and wasting time oand money tryingt o get things exchanged