It's because it's the same vehicle.. different paint jobs. Apparently they married up the loco with the chassis of one of the Soviet multi-wheel/steer missile carriers. When they tried it out, something broke and they left it as it was.
What really gets me is that if you look at the extra image FATROC posted you'll notice the metal plating over the hole left after the train coupling was removed. The brightly painted one still has this hole showing while the military drab one has what looks like the same cover over that hole. So, considering the green version is its current shape one can assume the bright one with the hole uncovered is the oldest picture. There that wheel is tuck like that. Then there is the picture still in the bright colours but with the hole covered and all wheels in alignment, the thing is actually on the road. And THEN there is the picture of it painted over, assumed the latest which has the wheel stuck in that same way again. Its weird. Its a completely minor thing that probably will never get answered, but it boggles my mind a bit.