This bug was found in version 1.19.83 with active sniffer experiments, snort sneaking and the 1.20 preview. When, in creative mode, I fly and hit my head on a ladder, it deactivates my fly and I fall to the ground. The following video demonstrates the effect of the bug. When I hit the ladder I always held the jump key to fly up. And also when I "entered" the scale the background turned black.