Search indexing currently reports failures to load objects to the log. This log is noisy, not concerning, not actionable, and not locally debuggable (it depends on the reporting user's entire state).
I think one common, fully legitimate case of this is indexing temporary files: they may fully legitimately be deleted by the time the indexer runs.
Instead of sending these errors to the log, eat them. If users don't notice the indexes aren't working: no harm, no foul. If users do notice, we'll run or have them run bin/search index as a first diagnostic step anyway, which will now report an actionable/reproducible error.