This bug is still in the 1.14.30 version of the bedrock edition. It is super easy to recreate. Just spawn a guardian in water a few blocks off the ground. If it is possible for guardians to fall off the water, about half the time they will just begin floating in the air. They will only fall if they begin firing their laser.
This bug still exists on 1.14.3. I have a very large wall of signs that I used for a guardian farm and it is incredibly laggy.