My problem seems related to yours. Perhaps my report will shed some light (for someone more knowledgable about Moodle than me !)
When importing ("restoring") a course from a Blackboard zip file (in which I exported everything about the course, including student accounts and discussion forums) I saw error messages such as
Could not get the course module for the forum
for each discussion forum. The rest of the Blackboard course did seem to get imported (but see below).
Afterwards I click on Forums and see a list of discussion forums... but clicking on any of them gives the
Course Module ID was incorrect
error, and indeed the number of postings is 0 in every case.
Backup and restore
BB Import yeilds "Course Module ID was incorrect"
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