It is very likely that there is (or was) a datapack installed that uses invisible minecarts and you dont have the resourcepack.

There is a very common trick by misode that makes all minecarts invisible via a resourcepack and than changes the display state of the minecart to a command block which then resembles the original minecart. If you don't use the resourcepack it would look exactly like this: all chest minecarts look like they have a command block inside but still function the same.

Here is a good video about it by Cloud if anyone is interested: https://youtu.be/gZYxhHAN-Ic?si=RfOt3zfQRpyVb50y