I've encountered this error, as well, and have reached out to my account team for more information. TAC informed me that they have no additional info beyond what is in the bug listing.
Issue impacts version 15.5, not just 15.6 as suggested in the bug listing. I've been advised that a change to how TMS scheduled spaces are handled is expected to fix this in mid 2019. Hopefully, it won't actually take that long.