Try this if you have errors opening a MIDI file, such as 'Corrupt MIDI file' or 'no MTrk header at start of track'. I have tried this on some old mobile phone generated MIDI (Sony Ericsson Music DJ).

fix_midi.py

# github.com/raphsilva, October 2020

# Have all your MIDI files in a 'files' folder and run this script from one level above that folder. 
# The fixed files will be in the same 'files' folder, renamed with a '_f' suffix. 
# MAKE A BACKUP OF YOUR FILES BEFORE RUNNING!

import os

for filepath in os.listdir('files'):

    filename = filepath.replace('.mid', '')
    print(filename)

    file = open(f'files/{filename}.mid', 'r+b').read()
    
    # This will remove the SEM1 part of the file, which seems to be the cause of the problem. 
    a = file.find(b'SEM1')
    b = file.find(b'MTrk')
    rem = file[a:b]
    file = file.replace(rem, b'')

    t = open(f'files/{filename}_f.mid', 'wb')
    t.write(file)
    t.close()

This seemed to snip off a little bit of the beginning, but made the SEM1 midi play just fine. Thanks!

@Maverynthia 😃