Bug While Farming CS drops by 100

I was just playing Gangplank and had 500+ cs then when I look I have 378 then Im back to over 500 it just keep reseting by 100ish each time when I finished the game it said I had 487 but in game I had well over 500.. my recorder stopped working mid game or I could post a link to footage.. just a fyi something is up.. cs is buggy,,