Minecarts transitioning from even to downward rails, derail above a certain speed

The slowest speed I could notice this on is maxSpeed 40. It could be a bit lower but it's impossible to see due to minecart position issues (MC-275565)

Reproduction Steps

• Build this setup (world download:

• )
  

  [media]

• Set minecartMaxSpeed to 100

• Close the loop and wait for the minecart to speed up (use /tick sprint)

• Change the rail shape with /setblock

Observed Result

• The minecart derails and flies through the air

Expected Result

• The minecart wouldn't derail since the track is continuous