(Edit - Millemissen beat me to it 😁 )
This is to do with the sound delay to sync with the picture on the TV when the video is processed for the screen. Sound is easier to process and quicker so has to be delayed to sync. (my simple version of the process)
There was quite a lot about that issue in the old forums. (google search Beovision sound delay) - but rest assured it is nothing to do with the surround module :o)
The best thing is to connect the speakers to the TV rather than the BS3000 and then they will play fine for your video sources. When you use your BS3000 to play CDs etc there won't be a delay when played through the TV (as there is no video to process). You can then use the BV5 speakers and the BL6000s for music.
You'll need to set up the speakers in the BV5 "sound" menu to tell the TV the speakers are attached (BL6000 will be on the list) and you will probably have to change the "option" on the TV and BS3000. You may have to add something to the Beo4.
My BV5 has 4 Beolab Pentas attached, DVD2 and a BS9000. When you press DTV it plays through all speakers, BS9000 does not turn on. When you press DVD it is the same, all speakers work and BS9000 does not turn on. Press CD or Radio and the BS9000 turns on and all speakers work (inc TV speaker - TV light goes green but screen does not turn on).
Stoobie