After quiting a world while flying with an Elytra all velocity is lost I am aware that for the specific issue of velocity loss there probably is a bug report
but as this is not the main point of this bug I wrote a new bug report.

sorry for rambling let's get to the Bug

1. What is the bug and how does it happen.

The bug (from my observations) occurs when you log out of a (Singleplayer-)world (I couldn't test for Multiplayer) whilst flying with an Elytra at high speeds, low(-ish) above the ground.
The first thing that happens is that when you log back in all momentum is lost,
secondly the flying sound keeps playing after landing (this seems to be somewhat inconsistent after a few atempts)
the sound stops either after a few seconds or after flying,
but returns playing when not in flight after teleporting through an End_Gateway.
I have included a test world for this Bug in the attachments.
Instructions on how to recreate it can be found there and I will give a shortend version here.

Step1: Get an Elytra
Step2: Fly up and fly about 5 Blocks above the ground
Step3: Pause and log out
Step4: Re-enter the world and you should hear the flying sounds
Step5: If Step4 fails which sometimes happens advance to Step6
Step6: Jump into an End_Gateway (only seems to work from below i dont know why but in testing entering from any other side didn't work)
[If you need the command for and End_Gateway use:

/setblock 0 56 0 minecraft:end_gateway 0 replace {ExitPortal:

,ExactTeleport:1,Age:195}

]

Side effects of the Bug are:

While the Sound Bug is activ pausing,
loging out of the World the bug was preformed in
and or opening another world Do not cause the flying sound to stop

Switching dimensions or using /tp seem to stop the sound with varying reliability

Closing the game completly causes the sound to stop although on restarting the Sound system doesn't load at all and has to be either reset through another restart of the game or F3+T
{{If anyone wonders how I found this bug,
I am currently working on an Minigame involving Elytra and End_Gateways and randomly came across this bug}}