Darius' Ultimate and Passive not working correctly.
On many, many occasions now, playing Darius, I have encountered these bugs a lot of time.
For example, when an enemy is on low enough hp to be executed by Noxian Guillotine and there are other team members present, attacking the target of Noxian Guillotine at the same time and I use Noxian Guillotine, I don't get the kill but my ultimate is reset and sometimes my passive is given, sometimes it is not, not working as intended to.
Other times the bug is simply not giving Darius his passive when he executes an enemy champion with his ultimate, another example of this is me attacking an enemy champion until they have 900 hp, I use my ultimate at lvl 18 when it has 1100 damage and I kill them, get the kill, get the ultimate reset but not the bonus AD passive.