Actually the audio for ROTJ Despecialized 1.0 is slightly out-of-sync. If what you’re seeing only starts after the final scene on Endor, and is most noticeable until partway through the battle on Endor, then this is what you’re seeing. The audio is about two frames off during that period, and then one frame off until the end of the film (I notice the two frame difference, but not the one frame difference).
You can either wait for the 2.x update or download a fixed audio track and mux it in yourself. PM me for a link to the fixed audio.