Bug(ingame) champ ult

I was playing normals in game againts a yasou mid and malphite jungle and I got camp mid. even during teamfights malp would ult me and this yasou waited so long ult. and his able to ult me when i reach grounds prob after 3 sec. everytime i landed on the ground by a malp ult, yasou was able ulted while I was in the ground. happen 10 times during that fight malp ults, yasou inexperience unable to ult fast, I landed on the ground BAM his able ult me.