During the design phase, it was decided to optimize BT reception, which is achieved by buffering digital signal streams. Since this takes a little bit of time, a slight delay will be the result. We have now optimized the software, so the lip-sync problem is no longer an issue. Video materials can now be watched with proper audio timing. Please check the product support page "downloads" tab for your headphone to check for the update files. If you experience delay, even after performing the update, please be aware that delays can occur for several reasons. For instance, the Bluetooth transmitter in a TV set can introduce delay. Also, some TV sets can cause timing changes if certain image processes are used. Try to disengage image processing, and check if lip-sync adjustment is available in your TV. With YouTube or other streaming services: In cases of lip-sync issues, it may also be a good idea to carry out a refresh of the source website. Always try more than one streaming source to determine if the delay comes from the streaming service or from you connection.