Can't seem to set individual item as due date "N/A" in Learning Plan

Content

We have one learning plan that we map to new employees every year. This requires they complete four course mappings within 30 days of us adding them to the plan.

Previously, when I mapped a course, if I didn't choose a due date, it would default to "N/A" and then the learning plan itself was due in the 30 days. For some reason, this year the courses defaulted to being due the date I added them to the Learning Plan. This has made these items show up as "overdue" for our users automatically because I mapped the courses in early January.