Had the exact same problem and got the answer here from Orzelek https://forums.factorio.com/forum/viewtopic.php?f=96&t=14563 I noticed in one of your videoes that your rail wagons had slots reserved for specific items. Example: Wagon has 30 slots, 15 are reserved for straigth rails, 5 for curved...

CHRIST that was a fast reply
Thanks a lot Orzelek, will try it right away

I noticed in one of your videoes that your rail wagons had slots reserved for specific items. Example: Wagon has 30 slots, 15 are reserved for straight rails, 5 for curved, 5 for big poles, 3 for rail signals and last 2 for rail change signals. I have tryed to find out how to do that in the game and...