Player's hitbox cannot update while within 1 block outside the world border

Player's hitbox cannot update while within 1 block outside the world border.

Step to reproduce:

1. Create a world and /tp 29999984 ~ 0

2. F3+B to enable hitbox

3. Try to sneak.

4. Try to glide with elytra (along z axis)

Expect result:

Hitbox update correctly (1.5 blocks tall when sneaking, 0.6 blocks tall when gliding)

Actual result:

Hitbox don’t update at all. You cannot sneak and still 1.8 blocks tall when gliding.

Notes:

Related to both MC-248304 and MC-181404 (Probably cause by the combination of these two bugs).

This bug affects X/Z between 29999983.7 to 29999985.0 for default world border size.

Other observed phenomenon:

1. Crawling from X=29999985 to X=29999984 will make you stay crawling even there’s no block above you.

2. Sneaking from X=29999985 to X=29999984 will make you look like normal standing and your speed is normal, but you are only 1.5 blocks tall.

3. Landing after gliding with elytra (from X>29999985) at X=29999984 will make you begin crawling.

4. Riptide into X=29999984 will make you look like normal standing and your speed is normal, but you are only 0.6 blocks tall.