Yasuo dash is granting invulnerability to abilities

I've had this bug occur in two ranked matches recently. this bug costed me the game in the second match. First occurrence happened when I ulted through yasuo as shyvana and went straight through him as he dashed through me. He was not knocked airborne or even damaged as my ult went clean through him. The second occurrence was when I dashed through yasuo with lightning rush as kennen and he dashed through me without taking any damage or being marked by kennen's passive. This led to me expending w on only minions that were near and subsequently losing a fight that was game ending.