A/V Sync errors, Lip Flap, and Lip Sync errors, are terms used when referring to the annoying situation when the Audio/Sound does not match the Video/picture.
The severity can vary by video content. The delayed video takes longer to process than the audio signal, and it is especially true when processing high definition video formats. Many devices now have adjustable A/V sync/delay settings in their menu system so you can manually synchronize the audio and video.
One thing that you can do if your devices do not have A/V Sync adjustments is to set the output video resolution of your Set Top Box/DVR/Cable Box, to match the 'Native Resolution' of your display/TV. (Native resolutions of modern day displays are 720P, 1080P and 4k/3840 x 2160P.)
Changing the Preferred Output Resolution on our DVR+;
On your remote, press "Menu"; Then select Settings>TV & Audio Setup>Display Setup>"Resolution" is the only choice on this screen. You must press "OK" to change the resolutions list "white", so they are selectable.
Now navigate Up/Down to the desired resolution.
When your resolution is highlighted Orange, press "OK". The display will go blank for a moment to change output resolutions and then the video returns and will be displayed at the new resolution.
Changing the preferred Output Resolution on our Stream+; Press the 'Home' button on the remote. Navigate down to 'Settings' and select it>Navigate down to 'Display'>Highlight 'Resolution'>Now you can choose the desired video output resolution. e.g. 1080p @ 60, 720p @ 60.