Thank you all for your input. The wheels jump when they hit the frog. I dismantled the 2nd radius where I am having the problem, I then reassembled the track, swapping points around. I have 2 right hand points connecting the 2nd and 3rd radius, The Mallard (only one I am running at present) only gets half way through the junction when it jumps off the track. I have checked that the table is flat and level and that the track and points are also level, it is smooth when I run my fingers over the joints. I can run the Mallard slowly in reverse and seems okay although the bogies wobble when passing the frog. I don't know why this is happening now, it running okay except the past couple of months. I can run the Mallard and Cock O the North on the outside radius without any problem, there are 3 points on this section and there are no problems with them. Peter