When rapidly teleporting an entity such as the player, if another command is also set to rapidly execute a command onto the player and if the player is moving at fast speed/has a speed or jump effect, the command executed at the player may execute in a spot the player was a few moments ago rather than at where the player is. This problem is partly related to MC-44823.

Sample Test:

1.Set a fast clock with a command block:

/summon FallingSand ~ ~1 ~ {TileID:152}

Then put a redstone block on top to start the clock.

2.Set up a teleport command and put it on the redstone block such as:

/tp @a 273 ~ ~

This example will constantly keep the player at a x coord of 273 but ignore y and z.

3.Set up another command on the redstone block, for example:

/execute @a ~ ~ ~ /summon FallingSand

Go to step 4a or 4b.

4a.[With Jump/Speed] Give your self jump boost or speed boost:

/effect @a 8 100 3
/effect @a 1 100 20

Go to 5.

4b.[With Teleport] Fly around, mostly fly up and down, and especially try falling down from a height without flying, as this appears to be when the bug occurs most often. The falling sand should occasionally appear at a spot you used to be rather than where you are at the moment.
No further steps from here.

5.[With Jump/Speed] Stand still and jump up and down holding spacebar The falling sand should occasionally, for example, remain on the ground rather than appearing where you jump. If this does not occur, move around and jump again holding spacebar, or stay still and wait a moment before jumping again.

Note: This does not seem to be a matter of lag, as if you were to continuously say something in chat while you jump or fly (possibly use a command block on the rapid clock with a /say command running), you would see that the chat would keep moving up even if the falling sand does not teleport to you. The rubber banding effect from MC-44823 can also be observed.