Locomotives cannot being placed on rails. They vanishes from the inventory, but re-appear in the inventory after world close and re-open.
The log says that the id value for 14 is duplicated.
The game does not crash, but the locomotive cannot be placed at all and this message spam the console.
I'm playing a singleplayer world.

Forge : 43.2.21
LittleLogistics : 1.4.0

https://pastebin.com/JGiyZVkQ

Could you try to reproduce this in a new world and see if it still happens?

Could you confirm that this happens with both types of locomotives?

Could you provide a full list of mods as well in case this is a compatibility issue

This bug is periodic and occurs only half of the time when the game launches :

1. Launch the game;
2. See the locomotives are placeable;
3. Restart the game;
4. See the locomotives are gone and are not placeable;
5. Restart the game;
6. Goto step 2.

Save and reload the world does not work, you have to close and reopen the game completely.
Both locomotives can't be placed, this applied to cars as well, but does not applied to the barges and tugs though.
Creating a new world or loading an old world does not matter, the bug still applied for both new or old worlds.

Can't reproduce with your mod alone.
There is the list of mods I have in my modpack: https://pastebin.com/mLBGp4sX