This issue was reported on Aug 4, I confirmed I also have it on a newer version on Sept 24, and yesterday another person confirmed on presumably the newest version.
It is now Oct 10. This issue is over two months old and spans multiple updates. Srsly.
Even offline, on singleplayer with no mods, the error still occurs in vanilla 1.16.3
Although the command only functions when I launch through MultiMC. If I use the launcher directly the command doesn't parse at all, see above.
When I use the command it says "no entity was found."
Running Java on MAC OS 10.14 using MultiMC launcher. Problem occurred in two separate worlds on two separate servers, 1.16.1 and 1.16.3 respectively.
Both are Minehut servers. Could the error be caused by Minehut or Bukkit?
I am also having this problem in 1.16.1 and 1.16.3. I created a new world to try to resolve this.
Please reopen issue.
I can't provide a seed but I can provide an update: the carts are present when the game is launched but are then despawned the way entities thar have not been interacted with despawn. I am on a new seed that doesn't seem to have despawned them (yet) but I will share it if they disappear.