A AdSense Help thread has confirmed reports from Google that some (not many) publishers may have had a hold on their account for about four months due to a bug. That means, these publishers were not paid for around four months due to an issue with a specific feature of the site.
As explained by Ashley from Google:
A small number of publishers have experienced this issue, whereby their account is on phone verification hold, but they cannot see the hold in their account. However, please be assured that the issue has been resolved on your account, and a payment for your earnings up to the end of November will be issued to you at the end of this month.
It is nice that Google will be paying out what is due to this publisher, but a four month delay and nothing extra for that?
Forum discussion at AdSense Help.
