[Client] Unable to redeem free hextech chests

I currently have 2/4 hextech chests that are redeemable. I've played a few games this weekend and today, winning some and finishing at S rank or having team members finish with S rank. Despite this I've yet to unlock chests for the champs I'm playing with. Is this a bug that has snuck in or am I just not blessed by the RNG gods?

Possible causes of error may be that I own all champs and have so far redeemed all chests possible, never having more than 2 hextech chests waiting to be redeemed. It may be that we're getting closer to the end of the season, so the size of my champ pool consisting of champs that are eligible for the hextech chest is going to be smaller than usual, maybe something server side is blocking me from being awarded with the hextech chests.

Please investigate.