DELAY in audio tracks

I use extensively MKVToolNix in film mkv files to add audio tracks and subtitles to obtain after remuxing a multi language film. I get the audio tracks via gMKVExtract and I edit them with another program (Audacity) to have a correct overlapping/synchronization with the base audio track. At the end of audio track filename there is always a DELAYxxmsec indication. Never given much importance as DELAY was always 0 or few msec. Negligible.
But now I met and audio track with DELAY 2800 msec . Huge! Even if the synchronization (visual overlapping of audio track images ) is correct, after remuxing the voice is out of synchro with the images. My conclusion is that I have to blame this 2800 sec DELAY.
Question : by whom and where is this DELAY established ? Is it possible and how to modify the audio track file to have a 0 DELAY?