My file cannot be opened

Dear,

I made the fourth movement of my first symphony a few days ago.
The file I saved calls | 1 Symphony M.4 Allegro.mscz |. Nothing wrong with, I think?
When I tried to load the file the next day, it said:
Kan bestand C:/Users/maart_000/Documents/MuseScore2/Partituren/Symphony no. 1/1 Symphony M.4 Allegro.mscz niet lezen:
Yes, it is Dutch. The translation:
Can't read the file C:/Users/maart_000/Documents/MuseScore2/Partituren/Symphony no. 1/1 Symphony M.4 Allegro.mscz:
The /Symphony no.1/ is the map. This map includes the four movements.
The first three movement do work well, but the fourth one does not. So it is not the map, which is the problem, I think.
I have had this issue before, this is the second time.

Note:
-I have had the soundfont 'Sonatina Symphony Orchestra', but I have not used this for my symphony.
The soundfont is not uninstalled yet.
-The instruments are (maybe this causes issues, but I cannot change them if I am not allowed to load the file):
Flute; Oboe; Clarinet in Bb; Bassoon; Horn in F; Trumpet in C; Timpani; Harpsichord (someone told me that this may cause the issue); First violin; Second violin; Viola; Violoncello; Contrabass

I hope that you can tell / explain me how to fix this. I am looking forward to here your response!

Kind regards,

Maarten Bauer