Hi Markey
The "front pony truck" is a bogie (just wanting to discuss the same thing.
It looks like this

It is held in place by one shouldered screw
A flat spring with 6 tongues ensure a ground return through the bogie (2 center ones pointed in red). 4 tongues ensure an appropriate pressure of the bogie on the rails(four external ones pointedf in blue).

If the bogie wheels dont rotate easily, then
- the bearings need cleaning and light lubrication
- the center tongues press too much on the axles
- the wheelset is partly disengaged from the bogie plastic chassis
Cheers
Jean