Defensive Mastery Bug [Gameplay]

So I was playing Malphite Support (cause why not I have a huge winning streak on him) and I was at about lvl 13 with some items and my armor and magic resist started to fluctuate constantly which I instantly assume has something to do with the new adaptive armor mastery.

My exact build at the time was Merc Treads, Sighstone, Targons Brace, Sunfire Cape, and Aegis of the Legion. With +15 AP, +12 MR, +8.2 Armor, and +3.7 Mp/5 from runes with. 4/26/0 Masteries. As soon as I increased my armor it stopped.

I believe this bug to become a problem in some situations due to the fact that you can have an ideal amount of armor or mr one second and then the next second get absolutely stomped cause your armor or mr went down.