I set up a pumpkin/melon farm on a realm and used a hopper minecart to collect the drops. Every so often, when the hopper is emptied and is supposed to start, it moves a distance of about half a block and then stops.

This is not dependent on chunk loading or chunk eborders. The minecart never crosses a chunk border, and I have seen this happen when I am 2 blocks away in the same chunk.

Attached below are screenshots of both the stopped minecart and the start/stop circuit.