Hoping someone here has a solution. I have a Lumia Icon 929. I have been trying to get it to a Windows 10 build for months. I can get on Windows Insider and get the build down, but after the gears stop turning, the phone shows a Windows splash screen for a second and then goes into an endless reboot cycle. I can use the Windows Phone Recovery tool to get the phone back and reinstall the Retail Windows 8.1 build, but that's not what I want. I should add that an update to 8.1.1 fails in the same exact way 9 out of 10 times. It kills me, because I have to start from scratch every time. Yes I can restore, but what the heck is wrong with the phone that it won't take an update like it should. SO irritating. The only advice I've heard that makes sense is to wait until the phone is completely charged and cooled off before you kick off an update. Surely there's a trick out there that will make the phone update like it should.
I would use the Windows Phone Recovery tool again and re-install 8.1.1 and don't restore from backup during setup. After the install is done download the Windows Insider app and join the insider program and see if it works now. If installed successfully do a phone reset via settings >about tap on reset your phone.
I had tried one of the earlier builds without a problem. Had to go back to 8.1.1 because of stability issues. Hoping the next release to the slow ring will be much better.
Primortal, thanks for the advice, but I've tried that. I think what's happening is that my hardware is very sensitive to heat. I was on another forum, and the folks there suggested I download any updates I want, but then sit on them overnight to let the phone get fully charged and cooled off. My phone was going into endless loops even with applying a minor update to 8.1, so this was happening outside of trying to get to Windows 10. I followed that advice last night after reimaging yet again, and waited until this morning to apply the minor update. It worked. I will try the same thing for the latest build of Windows 10 today.