This bug is when you have an elytra above the Y=255 or so you can start floating straight up. I have a video of this https://www.youtube.com/watch?v=OdDtRIvOeh0 but it does say optifine and 1.13 but I went and tested this on the latest update and it still happens.
MC-136070
Elytra goes straight up forever
Resolved
Duplicate
0
Duplicate of MC-135106.