Pressing F3 + B should show hitboxes. Try to make sure you are over the entity hitbox and not the minecart hitbox. Update if it doesn't work and you are making sure to be clicking on the entity itself.
Doesn't look like a vanilla server, so it can't be qualified as a vanilla bug.
Ethan Snider
Pressing F3 + B should show hitboxes. Try to make sure you are over the entity hitbox and not the minecart hitbox. Update if it doesn't work and you are making sure to be clicking on the entity itself.