This is still an issue on Realms at least. My minecart with hoppers will randomly stop and refuse to be pushed as though they have collided with an invisible wall, but only from one direction. If they come at the area from a different direction, it will proceed through the problem area as normal.
I have a screenshot of one of the times it happened. Here I have a powered rail on a hopper going into a block. It doesn't matter if it is powered the whole time or not. The minecarts will stop right on the edge of the powered rails and then will never go back on them by themselves unless I leave the realm for a few minutes and then come back. Once they work properly, they continue to do so until I leave the realm and come back again. Presumably you could recreate this by doing that over and over until you see the issue happen.
Picking up the minecarts, unloading and reloading the chunks, and replacing the rails does not fix it.
Jingletail
This is still an issue on Realms at least. My minecart with hoppers will randomly stop and refuse to be pushed as though they have collided with an invisible wall, but only from one direction. If they come at the area from a different direction, it will proceed through the problem area as normal.
I have a screenshot of one of the times it happened. Here I have a powered rail on a hopper going into a block. It doesn't matter if it is powered the whole time or not. The minecarts will stop right on the edge of the powered rails and then will never go back on them by themselves unless I leave the realm for a few minutes and then come back. Once they work properly, they continue to do so until I leave the realm and come back again. Presumably you could recreate this by doing that over and over until you see the issue happen.
Picking up the minecarts, unloading and reloading the chunks, and replacing the rails does not fix it.