Alongside all of the new features tagging along in Windows 10 and Windows 10 Mobile build 14291 for Windows Insiders, there are also a number of bug fixes and known issues tagging along. Since the build is being pushed out to both PC and Mobile, there are separate lists of issues and fixes for both platforms. Here's the full skinny on what's fixed and what's still broken:

What's Fixed for PC

  • This issue causing the notification area ("systray") to look out of alignment when turning on the "always show all icons in the notification area" should now be fixed.
  • We fixed the issue where connectivity to older Wi-Fi networks using the WEP encryption security method may be broken.
  • We fixed an issue where the "X" to close the "Find of Page" toolbar in Microsoft Edge is displayed off screen on 8-inch devices when in portrait mode.
  • We fixed an issue where the USB icon in the notification area was reverting to the old icon when ejecting drives.
  • We fixed an issue where clicking the suggested search in Microsoft Edge resulted in a URL to the search as the search string.

What's Fixed for Mobile

  • We fixed the issue where connectivity to older Wi-Fi networks using the WEP encryption security method may be broken.
  • We fixed an issue resulting in slower text input speed the more words were typed.
  • We have improved Word Flow recognition of longer words.
  • The All apps list has been updated to now follow the "Make Text Larger" ease of access setting.
  • We fixed an issue where Settings would sometimes list unresolved app names under Extras.
  • We fixed an issue where touch targets could be out of alignment in the Photos picker.

Known Issues for PC

  • We continue to investigate an issue in which some Surface Pro 3, Surface Pro 4, and Surface Book devices experience a freeze or hang and all input such as keyboard/trackpad and touch do not work. The workaround is to hold down the power button to force the device to hard-reboot.
  • Your PC may freeze when plugging in an Xbox One or Xbox 360 controller and other gamepads in this build.
  • If you use Hyper-V and have a Virtual Switch configured for your network adapter, you may see an error indicator (red-colored "X") for your network adapter in the notification area of your taskbar. The error indicator is incorrect and your network adapter should continue to work just fine.
  • We are seeing reports of some apps such as QQ crashing. We are currently investigating, and this bug may also impact older apps such as Windows Live Mail and Expression Encoder 4.
  • If you have Kaspersky Anti-Virus, Internet Security, or the Kaspersky Total Security Suite installed on your PC there is a known driver bug that prevents these programs from working as expected in builds from the Development Branch. We are partnering with Kaspersky to fix this issue for a future release, but at this time there are no known workarounds. While this issue is present, we recommend using Windows Defender or another third party anti-virus product of your choice to remain protected.

Known Issues for Mobile

  • If you reset your phone on this build (Build 14291) and restore your phone from a backup, restore will fail to install apps from your backup's apps list leaving blank grey titles on Start. If you delete the grey tiles and attempt to reinstall the same apps from the Store, you will not get app data restored. The next backup will over-write the app backup data as well. To avoid hitting this bug, avoid resetting your phone on this build. If for some reason you do need to reset your device on this build, don't restore your phone from a backup and you should turn off backup for apps and OS data to avoid creating a corrupt backup via Settings > Update & Security > Backup.
  • If you have a Microsoft Band 1 or 2 paired to your phone, it will no longer sync after updating to this build due to a system API failure that occurs after the update. If you want to get your Band syncing with your phone again – you can temporarily change the language of your phone as a short term workaround until we release a fix. Additionally, you can also choose to reset your phone to get out of this state – however you may experience this update issue again with the next build until we fix this issue. This issue may also impact Skype video and audio calls.
  • The Gadgets app will not detect the Microsoft Display Dock on phones running Windows 10 Mobile Insider Preview builds, and thus cannot update the firmware version. If you have a dock which has already been updated to version 4 then this will not affect you. If you have a dock that has not been updated, then you may experience some minor issues with USB-C stability. You will still be able to use your dock and Continuum.
  • There is a new option under Settings > Update & security for Windows Insider Program. This is a work-in-progress option to improve managing your Windows Insider Program settings on your device. Right now, if you go to this option it crashes the Settings app. Please continue to use the Windows Insider app to manage your settings for now.