Google did something different this year with the developer preview for Android N. And no, I'm not talking about the early release of the new version of Android. We're talking OTA's. Now instead of having to flash over the entire factory image to get Android N up and running on your smartphone, you can simply sign up for the beta and get the OTA onto your smartphone. Although the OTA is still quite large, over a gigabyte. You'll also get over-the-air updates for each developer preview that comes this summer, as Google says there will be a total of five this time around.
While OTA's for a developer preview are pretty cool, it's not all fun and games for everyone. Some users are reporting that the OTA is soft-bricking their smartphone. What "soft brick" means is that the device isn't working, but it is fixable. Some users have also reported that to fix the soft brick, they were able to sideload the OTA (as you would any other OTA) and get everything working just fine again. Typically this fix wouldn't work on most updates. But since this OTA is actually the entire factory image, it does work pretty well. Mostly because it's not meant for a specific firmware version, as you'd see with the monthly security updates.
The reason for the issue popping up hasn't been identified publicly by Google. But they are working on the issue - which means they likely know the reason but aren't talking about it just yet. We should have a fix from Google pretty soon on these OTA's. But for now, if you are having any issues, it'd be a good idea to either sideload the OTA afterwards, through recovery, or just flash the entire factory image. It may take longer, but will solve you a headache in the long-run.
It's also important to remember that these developer previews are just that, developer previews. So they will be buggy. Things aren't going to work 100%. We'd strongly urge anyone that's not a developer to stay away from them. It's definitely not a good idea to throw it on your daily driver. As there are many apps that don't work with Android N just yet.