A problem I've not seen before, but it would have a practical use unmodified!

If you couple it to another loco or two, they will overpower the defective bogie and drag the loco around ... and  the counter-rotating wheels should help to clean the rails.  That's essentially a technique I've used successfully to clean the running rails in coarse scale 3-rail O gauge, where a loco runs in the opposite direction if you simply turn it round.  (two 0-6-0s running chimney first dragging a third which faces tender first).  Cleaning the third rail isn't as easy, but if it's stud contact, the pick-up skates seem pretty good at polishing the studs anyway.

Presumably the worms must be handed to work properly, and so if someone mixes them up you get the starting point you faced!

I think the model is a bodge, as you suspected. The chassis is of the original type, two fixing screws to the body only. Later ones had an extra two screws at the diagonals to the ones on yours, plus two tiny screws, a pair at each end, securing the chassis to the loco nose. The body however is a later type, as it has the seam running horizontally across the nose, except for where the doors are - early versions forgot to do this and it's a real pain to scribe on (I've done several!)

A great result for your labour, I've several Bachmann Peaks of different variants and consider it to be one of their best, and most useful, locos.

John.

If they've come from eBay you can just return them and eBay will refund you over the seller's head, a lot of sellers (including me) put 'returns not accepted' but at least I mention any problems with an item I'm selling so the buyer knows what to expect.  Some buyers have fixed the problems themselves, particularly a PC monitor I sold last year, the menu button had broken inside and I kept getting menus flash up on the screen when I was trying to watch TV or a video, the local computer doctor claimed it 'couldn't be fixed', the buyer fixed it in five minutes!  It seems the majority of eBayers will try and sell you a dud but you don't have to accept it.  I've got five peaks by Mainline and Bachman, no such problems with mine or they'd go straight back to the sellers. 

I recently bought a blue Class 45 (no. 63 "Royal Inniskilling Fusilier" with a DCC chip, it wouldn't move on my 12v DC so I sent the chassis back for an exchange to an analog one.  I also changed the decals on my other blue 45 because the number was in the wrong place, though instead of '45 039' I made it no.49 so had to put '49' in four places, that one is "The Manchester Regiment".  My other peaks are D100 "Sherwood Forester", D1 "Scafell Pike" and D163 "Leicestershire And Derbyshire Yeomanry" all in green livery.  I'm modelling 1967-70 in East Anglia when diesel ran alongside the end of steam.  Yes, I know peaks didn't run in East Anglia unless on cross country duties, they could also change regions via the North London Line.

On 15/07/2023 at 22:05, Big_Bad_John said:

If they've come from eBay you can just return them and eBay will refund you over the seller's head, a lot of sellers (including me) put 'returns not accepted' but at least I mention any problems with an item I'm selling so the buyer knows what to expect.

I did contact the seller, and in this instance they sent me a refund ... without asking for the model back. I'm sure there's lots to read into that.

On 15/07/2023 at 22:05, Big_Bad_John said:

Some buyers have fixed the problems themselves, particularly a PC monitor I sold last year, the menu button had broken inside and I kept getting menus flash up on the screen when I was trying to watch TV or a video, the local computer doctor claimed it 'couldn't be fixed', the buyer fixed it in five minutes!

A lot of repairs sit in the "easily possible but not commercially viable" zone, particularly when you factor in paying someone to look into an issue, and the unknowns about how long diagnosis takes. People can do lots of things that businesses can't.