There are several instances in-game when your surroundings can block a prone, such as when close to a sandbag wall and shooting over it.
Other times tiny clutter objects can block a prone, other times it is not obvious why a prone is being blocked.

This is problematic however, as it is common to drop to the ground as quickly as possible when taking fire, it can and has lead to my death in-game, as it left me standing as I struggle to get my character to drop.

My proposal is to tweak prone to be unblockable and perhaps push away from any collision that would have caused a prone block, like in Arma 3.
It is better for gameplay to be allowed to prone in akward spaces than to have it completely block and lead to death.