Before the 1.64 update, for three years, I never seen such bug:
https://www.youtube.com/watch?v=Sgt8IYEfeVM&feature=youtu.be
If the stone is in front of you and you want to lie on the ground, in some cases you can do it!
All you'll see is a look into heaven.
BIS, Each your new update breaks the game, exactly the same as it improves.
Unfortunately, the game is not moving forward, because every patch adds new bugs.
**Now a player can not go prone, near a stones, when he's under fire!
Also the player automatically gets up from the prone position when lying on the ground! **
**This bug** - https://feedback.bistudio.com/T117123 **was ignored in last update!**
How In Arma 3 the player must escape from a fire? If he automatically stands up, when crawling and if he cannot lie next to the shelter! Such shameful errors are critical for the game, because this all can annoy players.
I hope, this all, must be urgently fixed in the next update - 1.66