Microsoft have pushed out a “Critical Update” for those users on developer preview. You will get this update whether you like it or not basically. You can update yourself or let Microsoft do it if you haven’t done so by October 27th at 3AM.
Bug fix? Security Fix? Microsoft says they’re doing this to test the update systems. You’ll get the latest build available for Developer for Preview (not Denim) which includes a range of fixes and ‘improvements’
I’ve noticed my 1520 doing a lot more random restarts (particularly just before freezing in certain apps. Which is weird since it never freezes). Hopefully this fixes that. My housemate has a 1520 on the same firmware and it’s not doing that reset so it might be an app thing or a memory card thing? I’m not sure.