The suggestion of Anonymous Monk that it’s because you skip the empty lines doesn’t persuade

And what is your suggestion, why do you think it happens ?

The code is fairly short and simple, and we only have live4tech's word that there are missing records

Your reworking of live4tech's code , aside from moving the 300,000-th line into the new file, doesn't change anything else -- if live4tech's original code had records go missing, so would your reworked code (they're virtually identical)