As your photo shot is front-to-rear then it's just as I suspected : Both your well-car & the last car of the MSTS LSE Series 7000 articulated train appear to be afflicted with the same problem but to a different magnitude because the rear portion of the well-car is much longer than the rear car of the Series 7000.

I can only suspect it has something to do with how the pivot points for multiple bogies have been specified for both these vehicles, but we will have to leave it to others to figure out what's going on & how to fix it.

Cheers, Mark.