I have also experienced this. The mineshaft seems to be generating twice, or at least the entities in the mineshaft. Because instead of one minecart, they spawn with 2. I did notice this didn't happen with every minecart in a mineshaft, so I am not sure how to reproduce it.
I have also experienced this. The mineshaft seems to be generating twice, or at least the entities in the mineshaft. Because instead of one minecart, they spawn with 2. I did notice this didn't happen with every minecart in a mineshaft, so I am not sure how to reproduce it.