Description:
When teleporting a player every tick relative to a stationary entity, the player's client can move around freely after the first teleport, but the server sees the player as still being at that entity. When the repeating command stops, it seems like the server snaps the player's location to what the player's client sees. To reproduce, use a command like /execute at @e[type=armor_stand, name=tpTest, limit=1] run tp @p[tag=tpTest] ~ ~ ~ running every tick.

Steps to Reproduce:

• Start up a server in any version after 1.13
• Connect to the server, not through localhost, as the bug only happens when the player has some ping
• Run /summon armor_stand ~ ~ ~ {CustomName:'"tpTest"'}
• Set up a repeating command running /execute at @e[type=armor_stand, name=tpTest, limit=1] run teleport @p[tag=lock] ~ ~ ~
• Give yourself the tag with /tag @s add lock
• Walk around
• Have someone else on the server verify that your character is stationary or set up commands to display your position on the server

Observed Results:

The player can walk around freely, while the server thinks they are stationary.

Expected Results:

The player should be kept in the same location, effectively locking their movement.

Videos:

I attached a video displaying the bug in 1.18.2 and another in 22w13a. I also showed how connecting to localhost results in different behavior in the second video.

Notes:

Notably, this bug does not happen when the player is teleported continuously to absolute coordinates.