Sometimes bugs just happen. Everything can be running smooth on the PTR, they bring it over to live and boom! everything goes haywire. Perfect example: the AH money bug. Mythic boss bugs are also hard to nail down as they have limited or no PTR testing and are only done internally so as to not create an unfair advantage.
Bugs happen; the ones that are reported should be fixed yes absolutely but ones that didn’t exist before bringing it to Live are another matter entirely
Edit: Limit are now at 25% on final boss after their reclear. This is their race to lose, they have a huge lead