I have an intermittent problem where some students in courses can't view the private questionnaire we have set up for their course (based on a template). They get an error message saying that it is closed or unavailable. They are not reliable in reporting the exact error message, and I can't seem to duplicate the problem myself.
I've checked the student role permissions, which are fine (also evidenced by some students having no problem). I've checked that the individual students with issues have the standard student permissions, which are also fine.
Where else should I be looking for the source of this problem?