Plarail Advance Issues

Hi guys,
I've heard reviews saying similar things where the trains have been reduced to a crawl after a short period of time.
There's always been a weight issue with the advance range which has led me to do the pictured modification.
Beyond this there other factors that affect the running of these trains.
The alignment of the axle and wheel can be quite bad on some power cars, turn the car upside down and check to see how much the powered wheels jump about when turning. This will reduce the traction the power car has at any one time and the rolling resistance when cornering will not help.
Also check that the curve sections of track are not warped as this will also effectively lift the wheels off the track.
The mechanism likes to attract hairs which will wrap round not just the powered axles but others as well. Hairs also get between the teeth of the sprung loaded gear and the power wheel which can make them slip.
I don't think it's a problem with a particular model, just luck of the draw.

Alastair