All three of mine were derailing r2 and 3 on an incline ( I have two helix on my layout ) the bogie has a u shaped bracket which makes contact with the NEM socket, I cut the bracket off, this allowed more throw on the bogie, however the sprung buffers were also fowling, I retracted them and put a spot of super glue on the back of them to keep them retracted, this seems to have fixed the issue, I didn't like making these modifications to these works of art, but they run on my layout now, which is better than them not running. In defense of the manufacturer, my layout does present challenges for rolling stock.