Hextech Chests are not being awarded appropriately for ARAM

I confirmed today that S rating do not consistently give hextech chests as they are supposed to. I am not sure if this bug is specific to ARAM, but this is where my wife and I confirmed the bug. We both were playing champions we own and have yet to get a chest with. 2 players achieved S in this particular game and neither of us received a chest. Just wanted to report this and see if anyone else has the same problem.