Flight controls disappear after climbing scaffolding

Verification builds:
1.8.0.8 Beta | Android: Yes
1.8.0.8 Beta | Windows 10: No

Summary:
Trying to fly from the top of scaffolding causes the flight controls to disappear, preventing the player from flying downwards.

Steps to Reproduce:

1. Load a creative world on mobile

2. Build a scaffold tower

3. Climb to the top of the tower

4. At the top of the tower, double jump to initiate flight

5. Notice the flight controls

Observed Results:
The fly up and down controls appear briefly then disappear. The only way to fly downwards again is to cancel flight.

Expected Results:
The flight controls should appear correctly.

Screenshots/Videos attached: Yes

Notes: