We don’t need to know what caused it. There is nothing a player can do about what caused it.
In this thread a Blue said they are working on it. That is the closest you will get to when it will be fixed. Blizzard generally doesn’t give an ETA as players tend to forget that the “E” stands for “estimated” not “exact”.
Where is that stated?
Or you could have followed the advice in this thread and made a ticket for it.
Edit:
The problem is affecting me too. I know not to blame Blizzard for not caring when I encounter a bug.