When you drink a slow fall potion and then stay near-still with an elytra then you start to rapidly flicker in and out of visibility. This happens when looking at yourself but it does not appear to other players in a multiplayer world (I tested via a LAN world so results might be different if on a server hosted via a different method)
This bug seems to happen whenever you either have very little speed in the Y direction, have next to 0 speed in both the X and Z axis or if you go at very fast speeds.
Also keep in mind that it is quite likely that slow falling might simply make it easier to trigger the bug and not actually be the source of said bug.