When riding a horizontal piston bolt in any cardinal direction, the minecart randomly falls off of the rails, or just stops as the pistons are pushing along. I think it has to deal with the hit box of the minecart missing the extending piston head. I've tried slowing down the repeaters but it still fails.

Expected result: In 1.12 and in 1.12.1, the piston bolt worked flawlessly and reliably like they do currently on java edition.
This is making nether travel very difficult and slow

It only seems to work on longer sections of track, like 20-30 blocks long. The diagonal piston bolts still work with out flaws, only horizontal. The original YouTube tutorial is no longer available so I attached a screen shot.