Sony released several major firmware revisions for this model. The most significant was the leap from v3.905 (Android 5.1) to PKG6.404.xxxx (Android 6.0.1).
Search for and download the latest firmware .zip file. firmware sony 43w800c
Resolving intermittent Wi-Fi disconnection or sound syncing issues. Latest Firmware Version Details Sony released several major firmware revisions for this