[GAMEPLAY] Unable to crit despite chance.

So, leagues system (as far as I know) for crits works like this. Crits not gotten in a row stack up. Crits gotten a row make the chance of getting one less. Essentially, if I crit once with 25% crit chance. I normally won't crit for the next three. Of course you can always get lucky. In this case however, it seems very odd. I was playing Tryndamere. I had full fury so 30% crit chance. I basic'd a Yasuo five times in a row. None of them crit with 30% chance. Normally you could say I was just very unlucky. But shouldn't the crit system in league account for that by making it impossible to not crit with 30% chance 5 times in a row. I ended up losing the game in ranked to this. Now, once I basic attacked a minion, it gave me a crit. Than suddenly I could crit on Yasuo. I think this may be a bug with the crit system, but I'm unsure. Steps to reproduce: Assuming it's a bug with the interaction between Yasuo's shield, and crit chances. Than step 1 is to play against a Yasuo. I was playing as Tryndamere at the time. Build up full fury than basic attack Yasuo say 5-6 times in a row. This may or may not occur again. I'm going to work on seeing if I can get it to consistently occur. WARNING: There should also be a very small chance you don't get a crit say 4 times in a row with 30% (as far as I know). I'm assuming this is a bug, however it could have been the 1 in a million chance of bad luck.