In file Th_quasibestprec5.msh, Erreur Lecture 6, good=0, bad=0, fail=4, eof=2 Line 40779

Hi guys.
Because of my research needs, I am trying to modify a mesh starting from the .msh file.
The problem is the following: sometimes I have no problem when reading by using readmesh the .msh file I have created while other times I get this error:

In file Th_quasibestprec5.msh, Erreur Lecture 6, good=0, bad=0, fail=4, eof=2 Line 40779

Do you have idea about the meaning of such error?

Thank you so much

I think the format of the file is wrong!
the error is fail