Windows 10 Insiders are now getting new build 14915.1000 and it fixes a number of issues. In order to download it on your phone, make sure you have enrolled in Insider program. For that, go to Settings > update & security > windows insider programme. And then, go to phone update under Settings to fetch it. Here is changelog of 14915.1000.
* fixed the issue causing apps to get stuck in a pending state if you move apps between a SD card and internal storage (either direction).
* fixed the issue causing Cortana’s text to speech capabilities to not work. Cortana should be able to read text messages out loud for you, tell jokes, sing, or give verbal prompts as expected.
* Changing functionality via Settings > Update & security > Windows Insider Program such as your ring settings should now work again on this build. For more information – see this forum post.
* fixed a compatibility issue from a recent platform change that causes apps such as Yahoo Mail, Trivia Crack, Google and the Skype Translator Preview app to crash.
* made a number of improvements to translations, including fixing an issue with Store app install notifications, where the wrong verb was used in German when letting you know to check out the app.
* updated “You need to fix your MSA” notification toast logic, so it will no longer notify you multiple times in quick succession.
* fixed an issue where examining Microsoft Edge’s advanced settings would result in subsequent downloads in Edge saving to the default locations, rather the preferred locations set under Settings > System > Storage.
* fixed an issue for Continuum-capable devices that could result in being temporarily unable to connect to a previously paired Windows 10 PC.
* Updated the settings for sounds so that .mp3 or .wma files downloaded straight from OneDrive or copied from File Explorer to the phone’s Ringtones folder will now display automatically in the list of available sounds for ringtones, alarms and notifications.
Last update for windows insiders on fast ring was Windows 10 Mobile 14393.67.