Was just playing a match and noticed the 3 second cool down to gain mana was not working most the time and I could stack it quicker then every 3 seconds. The item's cooldown animation would show in my invitory but everytime i used a skill it would just refresh the active cooldown and add another 4 mana.
additional notes: coop vs ai. i was playing nidalee. happened about 75-80% i used 2+ skills in a row

I was playing Blitzcrank and I also noticed very inconsistent CD timers for Tears, Arch Angel's Staff, and Manamune.