This glitch has been observed in some situations in version 0.14.0, but has now been worsening in recent updates. Sometimes, when I enter a world, some of the signs and item frames fall off for no reason. It can also happen when I am sprint-flying while the world is still rendering, and I can see the signs in front of me drop off. I have decided to report this issue as some players like me have maps which use signs and item frames extensively, and such cases of these items which I have painstakingly written on falling off due to some glitch makes it rather frustrating. Please look into this issue and try to resolve it as soon as possible!