[Gameplay] Penta kill timer bug

In a recent ranked game, I killed all 5 enemy players in quick succession but did not receive a penta kill.

Please see attached picture for a time-stamped chat log containing in-game announcements. At [21:42], 9 seconds after my triple kill (while being in combat the whole time), the game announces that I'm "unstoppable" instead of announcing a quadra kill. Then at [21:50], the game announces a double kill instead of a penta kill.

Perhaps the announcement of another player's kill streak interrupted the timer for my kill streak.