With each new build that Microsoft releases for Windows 10 mobile, new issues arise. And, that's a given. You can't deliver unfinished software to the public without expecting bumps and crashes. But, as each new build is available and then installed, and new problems are introduced, there's another, seemingly inconsequential effect that really might be the more important piece to Microsoft fully releasing Windows 10 Mobile sometime later this year.
In this latest build, Microsoft introduced support for non-Lumia devices for the first time. Specifically, the HTC M8. I'm an avid HTC M8 user, but I held off installing this build. My finger hovered over the "install" button for seconds that seemed like hours, but I could just never pull the trigger. And, now I'm glad I did. Many with the HTC have reported problems.
Despite releasing an update to the Windows Phone Recovery Tool just days prior to the latest build delivery that clearly added support for the HTC, the new functions just weren't enough. Microsoft has since delivered an updated version of the WPRT, but only to fix issues detected in Lumia Phones and not any issues resulting from hardware bugs (which is what comprises most of the HTC problems).
If you're insistent on continuing to participate and test new Windows 10 mobile builds, you'll definitely want the most current WPRT (which is now at version 2.1.0). You can get it here: Windows Phone Recovery Tool
And, you can always find the most current version on the Backup and Restore page for the Windows 10 Mobile Insider Preview: http://windows.microsoft.com/en-us/windows/preview-backup-restore
If anything, by the time Windows 10 Mobile finally releases, the WPRT should be a solid tool - until it's not.