Report a Summoner's spell Cool Down bug

Patch 5.22, when you have the Mastery "Insight" which reduce the Summoner'spell's CD by 15%, in the game, your flash will be 255 second CD instead of 300, After that, when you purchase Ionian Boots of Lucidity , the CD will reduce to 225 second, and then when you get Enchantment:Distortion, the CD is 191, which is right, but, after you die or sell the boots and buy it again, the CD will change to 217, and after then, when you sell the boots, the CD should go back to 255, but it will stay at 285 second , As a result I have the Mastery "insight" and it only reduce the my flash CD by 15 second, please fix it.