If both the audio and the video is in the same duration, as you have described, then you need to apply delay to the demuxed audio stream.

Go back to your mux’ing software (TSMuxer or MKVToolNix) and find the delay feature. Load the same video and audio streams.

If your remixed video has the sound before the actual time (ex. you hear spoken words before the lips move), then in the muxing software select the audio stream and apply a value in the delay box. Start off with a value of 100. This will nudge the audio stream forward.

If your video has the sound after the actual time (ex. you hear spoken words only after the lips move), then in the muxing software select the audio stream and in the delay box put a ‘minus’ sign and then the value (-100)–DO NOT PUT THE PARENTHESIS IN THE DELAY BOX. This will nudge the audio stream backward.

You may have to play with the values until you are satisfied with the results.

Good luck to you.