Pinion disengaging

[dunnyrail]

I'm building a rack line outdoors. Due to the contours of the garden (Wales isn't known for being flat, the very back of the garden is at chimneypot level), Gradients sometimes exceed 20%, though are always within the 25% limit specified in the literature. However, even at 20% I'm having some spots where the test light loco (2046) stops and makes a clicking sound. Any ideas?

I am trying to remember the issues that we had on the Ruschbahn with the rack section. As I remember it there were places where packing under the track was required to keep things all in a nice even line. I used a straight edge on the rail to find any dips which were mostly the issue.

One of the things that Andy did not like was the lumpy performance dropping down the incline, this was very much like the real thing (well the one at Jenbach anyway) and I guess must be part of the issue with a rack railway.