Android 4.4.3 KitKat was supposed to be a bug-fixing update to Nexus 4, Nexus 5 and Nexus 7. However, it delivered more bugs in addition to performance problems. Here are the issues reported by users to the official Google Forum about Android 4.4.3 update.
Bluetooth Connection on Cars
This bug appears to be related on the audio output during audio playback and active voice calls using Bluetooth on cars. You may see that the connection is working on the notification but nothing is coming out of the speakers and it is unknown if whether the dialler or the Bluetooth software is source of the issue.
Slow Downloading Speed
Nexus 5 Google Play Edition has been reported to suffer from serious downloading lags of content from the Internet. Downloading of online newspapers may take five to ten seconds after the update which originally a few seconds only. Browsing speed is also affected by the slow downloading speed.
Missing Gallery Contents
Contents on the Gallery app may be missing after updating to Android 4.4.3 KitKat. Users may find the files inside the file manager but absent on the Gallery application itself. One workaround is the reinstall Google Plus in order to refresh the app.
Photos App Backup Issue
Similar with the missing Gallery contents, Photos App connected to Google Plus may fail to perform automatic backup. Uninstall the updates of Photos App and reinstall of the updates may resolve the backup issue.
3G/HSPA+ Disrupted Connection
For 3G users, a disruption may occur during mobile data connection. The bug causes the mobile data connection to stop regardless of signal strength and requires a restart or toggling the Airplane Mode to be resolved. However, the solution is only temporarily as the issue may still occur anytime.
Video Sharing to a Device
In addition to audio issue on Bluetooth with cars, a complaint reported that it even affects the video playback when sharing files with other devices using Nexus 5. The audio output is only retained on the built-in speakers rather than streamed on Bluetooth or NFC devices. Using other media apps may also not work to resolve the problem.
Unusual Battery Drain
Some users are also complaining about unusual battery discharge with Android 4.4.3 KitKat. There is no known specific application which causes the sudden battery drain after updating to Android 4.4.3.
No Voice Call Notifications
A rare issue has been reported that Nexus 5 does not ring when someone is calling. The user may experience no ringing sound or no notifications of missed calls but the caller can hear the device ringing from the other line. Rebooting the smartphone can temporarily resolve the issue.
Bad Voice Call Quality
If you manage to retain an incoming voice call, you should listen closely to the quality. Some users are suffering from bad voice call quality and can describe as "you seem far from your phone." Callers may be unable to hear users of Nexus 5 due to low audio quality or poor reception.
Front Camera Problems
Some users are having issues with the front-facing camera on Nexus 7 including "a darker" camera, unable to be recognised by the Face Unlock feature. It seems like that it only affects the Face Unlocking security under Portrait mode, not Landscape mode.