Microsoft released a new Windows 10 Mobile preview today. Like the last one, there are no new features in this new build for phones, as the company is preparing for the mobile operating system’s launch.

Microsoft calls this a “really great build.” That said, there is a caveat for those who installed the previous build and subsequently factory-reset their phone: Make sure to back up before you upgrade.

Microsoft plans to launch the first Windows 10 phones, the Lumia 950 and Lumia 950 XL, this month (dates vary widely depending on your country and carrier). This may be the build new Lumia owners end up seeing, as the main showstopper bug only affects testers.

Warnings aside, this build fixes the following issues:

  • The issue that caused the Start experience to become corrupted (garbled) after upgrading and restoring a backup from a phone that had a different resolution.
  • You should now be able to set your default save locations via Settings > System > Storage and it will correctly reflect the current storage settings. Your SD card should no longer show up as a garbled name in Storage settings either.
  • Moving apps to a SD card should no longer cause those apps to crash.
  • You can expect improvements to the Messaging + Skype app through both app updates via the Store and also on the server side.
  • There should be less resuming/loading text when switching apps.
  • The physical camera button should be working again if it wasn’t working for you before.
  • Apps and games should download from the Store more reliably.

Today’s update bumps the Windows 10 build number from 10581, made available to testers on October 29, to build 10586. Unlike Windows 10 for PCs, which launched on July 29, Windows 10 Mobile hasn’t been released yet — it’s behind in terms of features and polish compared to its PC counterpart.

Build 10586 has the following known issues:

  • The filesystem becomes partially corrupted after doing a factory reset on build 10581. Upgrading to Build 10586 will cause your phone to go into a reboot loop. To recover, you can use the hardware key combination to reset your phone or use the Windows Device Recovery Tool to go back to Windows Phone 8.1 and then upgrade to Build 10586.
  • Deploying Silverlight apps through Visual Studio to your phone still won’t work in this build. This issue will be fixed with the release of Visual Studio 2015 Update 1 on November 30.
  • There is a known issue where the tile for Insider Hub still remains under All apps but doesn’t open. Insider Hub isn’t included either, but will return in a future build.

Microsoft still plans to roll out Windows 10 Mobile to existing Windows Phone users in December.

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