When I edit a Local Filea song, my iPhone keeps the same length of the original

[drwpeak]

Plan

Premium

Country

UK

Device

PC, iPhone

Operating System

Win 10, iOS 12.2

My Question or Issue

I usually edit my local files songs, but each time I do and try downloading them on my iPhone, the length is still the same as the original? So e.g. one songs track length was 3:34 but I extended it to 3:53 - my iPhone still thinks to keep the track length to 3:34 and just skip to the next song after it reaches that point. What should I do?