The cluster points at a URL that is not among the pages found. Either a version was removed and the template still declares it, or the addresses drifted apart.
The finding reads:
info hreflang-unknown-target the alternate … is not among the parsed pages — reciprocity cannot be verifiedRemove the addresses that are not among the site's pages from the cluster, or correct them. Right now the cluster points at nothing, and a search engine is entitled to disregard it entirely.
Reported per page even when it is common. Appearing on many pages is the nature of this finding rather than evidence of one template defect, so collapsing it would hide real work.
pipx install indexgap
cd your-project
indexgap init
indexgap checkThen indexgap brief turns
every finding on this page into a work order in indexgap-briefs/,
with the thresholds the result has to satisfy and the command to check it.