I've dug out my old train set and am having some bother getting it going.
The trains will move (a Flying Scotsman, which barely moves at all, and a Class 59 diesel which will move) but very slowly and often need a push to get over the points. Even at full speed on the controller, a Hornby R965, the trains edge their way around.
The set hasn't been used for about 8 years and has been stored under a bed. The track is all connected properly (though some of it isn't a tight fit) and set up on a hard table. The layout is a basic loop with two sidings.
The 59 diesel has improved after a few pushes round but is still running at about a quarter of the speed it should and the movement is jerky. The A3 barely moves at all.