How to create:
Place some powered rails in 1 deep water and then place 1 minecarts in it
Ride the minecart for few blocks and jump out
There you have it minecart gone

How to fix it:
Press F3 + B to show hitboxes and the minecart will appear back
It may stay it may go away as soon as you disable hitboxes

What should happen:
The Minecart should not disappear (Though the entity is there and u can interact with it)