The options were correct.

Please find the intitial .mat (the one I creating while debugging my .m) and the .mat after the  bus error.
When I try to open the second one in matlab I have this error

Error using load
Unable to read MAT-file C:\Analyses\xxx\BATCH_12012021.mat. Not a binary MAT-file. Try load -ASCII to read as text.

I hope we will manage to make it work,
Best,
s.