by Mary Cooch.
I don't know the answer to this (sorry!) as I don't use external database enrolment method but I would have thought not being able to unenrol them manually was expected behaviour, rather than a bug. If you enrol them via a database you would expect to unenrol them via the database too. On a slightly similar note, it's like this with groups that have been created with enrol plugins like IMS enterprise- or cohorts that have been added in bulk to a group in a course - you can't manually remove members from the group; you have to go back to the original source, ie IMS Enterprise or the cohort to do this.