Today, Microsoft released Windows 10 Mobile Insider Preview build 10586.122 to the Slow and Release Preview rings. The update is supported by all devices that can currently run the Windows 10 Mobile Insider Preview and a few extras.
It doesn"t contain any additional features, as it"s a cumulative update; however, there are quite a few fixes. Here"s what they are:
Improved Kanji input experience while using Continuum.
Improved the speed in which thumbnails appear for portrait videos.
Improved Internet Sharing on select mobile network configurations.
Fixed an issue in Microsoft Edge that prevented Word Flow input on some sites.
Fixed an issue that previously prevented the option to “Close all Tabs” in Microsoft Edge from closing all open tabs.
Improved IMS registration on select mobile network configurations.
Fixed an issue where adding your MSA during OOBE would fail and prevent the account from being re-added after the failure.
Improved the email sync experiences when connecting to Wi-Fi networks with a captive portal.
Improved data connection profiles for dual SIM devices.
Updated background processing of multiple changes to improve battery life of devices.
Improved quality of video record to SD memory cards.
Improved video recording audio in some cases.
Improved overall OS reliability, including reliability of the Start screen, app updates, and the Windows Feedback app
Improved Alarm reliability.
There were no known issues listed.
Source: Windows Blog