I think that is due to buffer-filling when arming tracks.
I seem to remember having seen that before. But also seem remember that it are actuallly very small amounts of difference. Nevertheless, that doesn’t solve your problem.
Are you sure you have recorded in the Broadcast Wave format!?
If so, then maybe a BWV header tool can help you.
If the file format was “regular” .wav, then I am afraid you are out of luck.
Fredo