Using The Google, I learned that merging mp3 files that were encoded with variable bit rate (VBR) may produce a mp3 file with an incorrect estimate of the total playing time for the merged file.
I found an interesting article that describes the useful utility “wxMP3val” , Integrity Checking & Repairing Tool for MP3 files
Here is a link to the description: https://www.hecticgeek.com/2012/05/wxmp3val-mp3-integrity-checking-repairing/
