Hello.
I made a BP with train carriages witch follows a spline. In editor mode all carriages are placed in the correct position. When I start the game carriages sometimes is in correct position, other times are too distant from the other one or one compenetrate the other. Many times altough in the correct position, some carriages during the animation compenetrate the other.
What can I do?
In editor
In game
All movement are generated from a timeline which is the same for all carriages to prevent some difference of movement.
For example: couple between the two carriages is ok
Then it creates a gap between the following carriages
Anyone could help me?
Does this happen only when the train is moving around a curve, or does this problem also occur on a completely straight section?
Definitely the problem is in how geometry works. 
When the train moves in a straight line, you can simply add an offset to each car, and they will maintain the same relative position.
But on curved sections, it is necessary to additionally shift the cars relative to each other along the spline so that the distance between them remains constant.
This problem is described here. And unfortunately, nothing better than an approximate selection of the point has yet been invented.
I also spent a lot of time making my train to Unreal, and settled on this option.
When you talking about offset do you mean add a delay ( in my case) before timeline which sets the animation ? Ok anyway I will try to read your link tomorrow because now I am so tired then it seems arabic 
No, you need to add an additional distance that each cart should move, depending on where it is relative to the previous one.
