We've been using Turnitin's Direct v1 assignment since 2012 and only recently had a very strange occurrence where a student submitted two assignments for where there should have been only one submission possible, resulting in an aggregate grade for that specific assignment. We did check the settings, only one submission is allowed (both submission for this student are labeled Part 1). We also tested to see if submissions could be made in duplicate simultaneously through different sessions/browsers (they cannot be).
We have no idea how it happened and it appears to be isolated to this one student/one event.
Screen shot below, anyone else encounter something like this?