Bachmann repair service

[Nokonium]

I am inexperienced in taking OO gauge models apart and when I burnt out the motor on a Bachmann A1 "Curlew" loco I dipped my toe in and quickly pulled it out again. I was asked to remove the DCC sound as it wasn't factory fitted, problem - one of the screws on the tender is directly under an axle. Not knowing how to proceed I contacted them and sent the Curlew as it was.

Pleased with their customer service and although it took a couple of weeks to come back I was quite happy.

Then I started to run Curlew on my layout and the tender kept derailing, points, curves, level crossings with and without coaches. It ran perfectly at what I regarded as express speed before I sent it for repair and now it wouldn't (forgetting that I had left it running was how I burnt out the motor). Couldn't understand why it had started to derail. Researched causes of derailing, checked the track for obvious problems, none, so had a very close look at the tender. Something wasn't right, the engine I sent away was a pain to handle and put back on the track because the connector between the engine and the tender was attached to the engine but not the tender, the connector went through a slot at the front of the tender and located on a stud, no screw fixing, just a loose fit on a stud. The tender I was looking at had a screw holding the connector in place. The engine was definitely the one I sent away but the tender definitely wasn't.

After doing a full service on the tender, wheel gauge, wheel cleaning and axle lubrication Curlew now runs as well as it used to do. I wonder if Bachmann damaged the original tender removing the axle to get the screw out?