The solid block doesn't need to be immediately behind the portal block. At higher speeds (for example maxSpeed 100) the block can be 2, 3 or more blocks away from the portal block and it will still stop your momentum.
This ofc doesn't make sense since the minecart went through the portal before it could have collided with the block.
Steps to Reproduce
Set
minecartMaxSpeed
to 32 or higherBuild a rail track leading to a nether/end portal
Place a solid block immediately behind the first portal block the minecart will encounter
Compare the results with and without the solid block
Observed Results
When the solid block is present you appear on the other side of the portal with no momentum
Expected Results
You would keep your momentum
Relates to MC-275558
Update: Can confirm.