Enrolment

Hello
we have LDAP authentication turned on so that when a logged in learner enters a course new to them they are automatically enrolled into the course.
We upgraded over the summer to 1.9.5
We also turned off the message that said 'you are about to enrol on this course, are you sure' as it put a lot of people off and caused confusion.
Now when learners go into a course new to them sometimes they are enrolled and some times they aren't. There does not appear to be a pattern, other than turning the message back on - any thoughts how to fix it please?
Thanks