Weird Fleischmann ICE-T 7460 engine behavior

[Yavianice]

I'm starting to really doubt myself....

 

I have ordered a replacement engine from Fleischmann several times for my ICE-T (7460), but in all cases, the engine goes significantly faster in one direction than the other. I do not receive an answer from Fleischmann, so I keep returning it and then getting a new one (sealed in box). Changing powerpacks/orientation/hooking it directly up to the powerpack does not make a difference.

 

Am I doing something wrong? Does anybody else own the ICE-T from Fleischmann and can they confirm this odd behavior? Am I going insane?