Minecarts used in farms that should be constantly moving seem to randomly be stopped when reloading the chunks. All the carts in question where I have noticed this are contained entirely within one chunk, running under farms. It does not seem to matter if it is on powered rails or not. The stopped carts usually start moving again when bumped, but it is incredibly frustrating to have to remember to check 15+ carts every time I return. I had an additional 16 carts running under other farms, but after those were all stopped over the weekend, I replaced all those with alternatives.

This might be related to issue MCPE-185643 (minecarts freeze on a block and can't be moved), since that also happened to me and didn't clear until I restarted the game the next day, but this issue is not exactly the same, as often a bump resumes the cart's motion.