I'm not sure when it happened, but a ghost copy of one of my carts has appeared on the track. it is invisible, but has clipping, and is immoveable. I've removed all the blocks under it and it did not fall, and I have placed lava in it's location and it was not destroyed. I can not rightclick it either, as it seems not to have an entity in the world.

humm, possibly try using the kill command to get rid of it (I think you can limit it to certain entities, but be careful as you may loose the other ones.

I wonder why this has happened? is there anything in the log? try re-logging/re-starting the server? I know of some bugs that are still in popular mods that cause invisible client side entities, I wonder if you have this bug, a restart should tell.

relogging with the client did not fix the issue. it looks as though reloading the server did infact fix it, as well as duplicating the minecart that the ghost generated from. unfortunately I am only a player on the server and have no access to logs or other anministrative content.

Humm, I’ll leave this issue open for a bit to see if anyone else has the same issue.

I'm fairly certain this has happened twice on the server I am playing on. I logged in one other time and found that my farming cart had duplicated itself as well.

Using Steve's Carts 2.4.29.132 for 1.12.2 as part of the Sevtech pack, seem to be having the same issue. Found that my tree farm had some "phantom" entities on the tracks blocking the carts, they did seem to be moved by pistons but also could not be destroyed by lava and didn't have clipping with players.