Yesterday Microsoft released Windows 10 Insider Preview build 14393 to insiders on the fast ring. This build only fixes a few things, with most of the improvements and fixes geared towards mobile. Of special note is the resolving of an issue that was causing battery drain on older devices like the Lumia 535, 640, 735, 830, 930 and Icon. It also fixed an issue causing Voice Recorder to not show up consistently as an option for Call Recording. An updated driver will roll-out via Windows Update soon that will fix this.
Source: https://www.bleepingcomputer.com/news/microsoft/microsoft-releases-windows-10-insider-preview-build-14393/