What's that THUD sound? It's your Lumia's best feature after unflashing Windows 10

Microsoft has temporarily pulled builds of Windows 10 for certain Lumia phones from the Windows Insider program, after some customers reported that trying to roll back to Windows Phone 8.1 killed their mobes.

"We are seeing some reports of failures on Lumia 520/525/526 devices when trying to roll back to Windows Phone 8.1 using the Windows Phone Recovery Tool," Microsoft forum manager "Jason" posted to the Windows Insider discussion group on Monday. "We are pausing build availability for these devices temporarily while we investigate the issue and work with customers who have reported problems."

The "failures" in question appear to be catastrophic, with owners of those Lumia models reporting that the Recovery Tool rendered their devices completely inoperable.

"Within 5 minutes recovery fails. It told to restart phone but I can't. And now I just have a red screen where writes 'Nokia'," wrote one forum poster who tried it on a Lumia 525, adding that the red screen persisted for at least five hours and the button sequence for a hard reset wouldn't work.

Another forum poster wrote, "After a second try, it went completely black and now does nothing. The recovery software says the phone ID is missing (the hardware is still recognized by Windows)."

The glitch is a setback for Microsoft's effort to bring Windows 10 to phones, which always appeared to be on shakier ground than the full-blown version for PCs and tablets. When Redmond launched its first Technical Preview for phones in February, it described it as "the earliest publicly available preview we've ever done for Windows on phones."

That first preview only supported six Lumia handset models. The three models that Microsoft has confirmed as experiencing failures only gained access to the preview program with the very latest Windows 10 build, which shipped last week.

This may not be the end of it, though. That most recent build opened the Windows Insider program to a total of 33 phones, and according to posts on Microsoft's forums, some customers have been experiencing similar failures with different Lumia models from the one mentioned in Monday's recall.

It may even turn out that it's the Windows Phone Recovery Tool itself, and not anything particular to the Windows 10 Technical Preview, that's the problem.

"Same [problem] here, but I hadn't even installed Windows 10," a forum poster wrote. "I simply tried to recover my phone using the Windows Phone Recovery Tool and it got bricked. Now it won't even turn on or do anything. It's completely dead."

Microsoft has given no further updates on the matter so far, but Lumia owners – especially those with the abovementioned models – are advised to proceed with caution when flashing their devices with the Windows 10 Technical Preview. Many other users are reporting problems ranging from apps crashing to their phones becoming nearly unusable, which is why many of them chose to roll back to Windows Phone 8.1 in the first place. ®