From my experiencre this kind of error appears when you mistype one or more instructions (or use the wrong syntax). But it is hard to be more precise without seeing your code.
Apparently the error disappeared. I logged in my account today after a couple of days and now it runs correctly. I don't know how tho. I checked for the syntax because I'm using english codes but changing the stimuli in italian since I need it for my research and it was all correct. I wrote an email to firstname.lastname@example.org since I was in trouble, maybe he saw it and fixed it.
Thank you for replying anyway, I appreciated it Have a nice day