Hello,
1 – How are you extracting it? Is it being converted to another format? A 1 second discrepancy over a 90min movie represents only a 0.0185% (x= 1/(60x90)x100) error. In the process of conversion it could have moved a little.
As such, it sounds like the extra second is coming from your extraction method, not WavePad. Test for this by extracting the audio then trying to “slot it back in” without making any changes.
Cheers
M