I did assemble this kit yet but maybe @Tricia12 or @SunnyCee can help you because the already did it ( I think Sunny had the same problem or similar) 
You need to check the gears on the train. I once had one get stuck and had to take it apart to fix it.
Check whether the tree branches are positioned correctly so they don’t catch on the top, and make sure the rail is well aligned so it doesn’t get stuck underneath. You might need to take it apart a little, just before the section that covers the rail, to see if that helps you fit it properly so it runs smoothly without getting stuck 
Oh no…I hope that you can find a solution to your problem. This looks so nice when finished.
I had the same issue. You need to tighten down your the pins under your train so it has zero wobble.
This is the part you need to adjust. Just keep tightening and adjusting the pins until your train runs completely tight. Zero wobbling or shaking.
Here is a video before I adjusted the pins. You see the train is shaking around. This is what you DON’T want. https://m.youtube.com/watch?v=LMRDz7q7n_0
Here is after I adjusted the pins. The train has to stay on a tight track because it passes extremely close to scenery.
My tram is a little wobbling but never got stuck. But I would think of the pins. Tighten it enough would help.
I hope Sunnycee’s tip helped. I haven’t built this structure yet, so unfortunately I can’t help you.
@SunnyCee thank you so much 
Good luck. I hope you are able to get it dialed in. If not, @CustomerService may be able to help you.
Hello! It needs to be reassembled. The circled part may have jammed the train—you can adjust the train’s angle slightly. For the part indicated by the arrow, please apply a small amount of lubricant to both its inner and outer sides.
I’m sorry I can’t help you with this but I think Sunnycee’s and CustomerService response might be a big help to resolve the issues.