https://musicbrainz.org/cdtoc/9IJicubE2sms4mejeMo5KUlXMN8- has existing discIDs. By clicking "Move" you get, say, https://musicbrainz.org/cdtoc/move?toc=58257 - that "toc" parameter is in fact a rowid for the medium_cdtoc table. That still gets seeded to the release editor if you click "Add a new release" though, but it's obviously an invalid cdtoc.
Given there's no way I can see right now that a CD TOC could be confidently moved while adding a release (rather than just seeded but still kept in the original release), we might want to just disable seeding a new release from cdtoc/move in the first place. If not, we should load the actual TOC and seed that.