Re: loading loop on windows 10 mobile build 10166!!!
I upgraded from 10149 and experienced this issue. I managed to get into Settings and perform a backup, and performed a hard reset. I almost went with a clean install, but decided to restore my backup, and after it was complete, I was greeted by the Start Screen. I worked with 10166 since yesterday, trying different things, configuring it to my liking, and restarting my Lumia 1520 a few times. Every time, the Start Screen appeared correctly. All the while though, apps were continuing to restore, and then this morning, after a restart, I was faced with the "Loading..." loop. I'm leaning towards it potentially being an app, but that is merely gut instinct at this time. If I knew which one it was, I could uninstall through Settings -> Device -> Storage, but right now it'd be a crap shoot, just uninstalling at random, and then restarting each time just to confirm. It could take hours or days. I know that with... 10149, I believe it was? That some were reporting 1Password was possibly causing similar issues to this, so it wouldn't be unheard of. I'm not using 1Password this time though. I'm leaning towards the culprit being one of the old 8.1 apps with deeper ties to the OS though, like Glance, etc. I suppose that I could start with those. I'm currently moving all apps to my SD Card too, in some random, unsupported hope that it might work. At least I'm not alone!