This happens in both Survival and Creative. I was searching for a stronghold in a creative world and went from gamemode 0 to 1 (survival to creative) after testing mob tracking in creative mode. Jumped only once while trying to fly, and my camera went into slow mode as if I hit f6 or whatever.

Has happened numerous times while adjusting my speaker volume via keyboard dial/keys (it's not the keyboard). It's also happened while tabbing out to change a song on a music player, or just minimizing/going into full screen. I've had it happen just from changing the difficulty in-game, from changing my render distance, the smooth lighting level, particles, and volume bars in the options menu.

Another bug, which I'll make a new post for, is that none of the f6-10 keys (I cannot remember which ones do what) change the camera speed/type. So you can't even fix the issue in the snapshots just by pressing a key.. So extremely annoying.