Issues with HandbBrake
1. Media Player Problem
It may have handbrake audio delay using some media players while playing certain format of video. Try VLC, KMPlayer and other popular media players.
2. Hardware is Out-of-date
An old computer with out-of-date hardware will easily result in "HandBrake audio falls behind video" issue.
3. Original Video is Out-of-sync
Don's ask how to fix Handbrake audio out of sync problem, the A/V of your original video itself may be already out-of-sync.
4. Framerate Problem
HandBrake designates "Variable Framerate" as default setting when you encode videos or rip DVDs. In fact, it may probably cause HandBrake audio sync issue. Select certain "Constant Framerate" to fix Handbrake audio video out of sync.