Microsoft released its most recent Windows 10 preview, build 16257, for PCs in the Fast ring on August 2. Last week, its plans to roll out a newer build were hindered by a 'blocking bug', but it had aimed to release a new preview sometime this week.
However, those plans have been ruined by the discovery of another show-stopping bug. Yesterday, Windows Insider Program chief Dona Sarkar tweeted: "We've hit a rollback bug with our build candidate. Keeping [an] eye on more data so no Fast Ring build release today."
Today, Dona tweeted again, confirming that more time is needed to squash that bug:
That means that the next Windows 10 Fast ring build won't be released until Monday at the earliest, almost three weeks after the last PC build rolled out. It also seems unlikely that a new Windows 10 Mobile build will be released before then; in response to an enquiry on Twitter, Dona said: "We generally try and flight [PC and phone builds] together to make it easier on our flighting and feedback systems."