I don't want to write a book here, so i made a YouTube Video for you:
Floating in Minecart Bug
MC-117913
When a minecart is summoned by command, the hitbox is doing crazy and annoying issues
Resolved
Duplicate
0
RatorLP
(Unassigned)
Unconfirmed
Minecraft 1.12 Pre-Release 5
Retrieved
It looks like you're summoning the minecart one block too high. Change your command so the minecart is summoned one block lower.
Also, why it is so difficult to just write "if you summon a minecart, its hitbox is offset by a block"? You can't expect the devs to watch a 10min long video just to understand a bug report.
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