[GAMEPLAY] Master yi passive not critting at 100%

hi Riot! so while playing master yi in a custom 1v5 bot game i found that his double strike first strike and the first auto attack after the double strick (the half damage attack crits normally, the one before it and after it don't) do not crit against monesters (baron/dragon/scuttle) even though i had 100% crit chance.

it crits normally on champions. so i tried again and just stocked on cloaks and it crit normally.

which means its probably item related ? my items were : infinity edge, rapid fire cannon, blood thirster, static shiv, blade of the ruined king and essence reaver.

how to repeat ? easy build the above items on yi and attack a monester.