Search index updates sometimes get dropped

Search index updates for edits/merges today have been dropped in at least two cases that I've kept track of. In both cases, edits/merges before and after the missing ones did correctly appear in the search index.

NOTE: This is separate from the updates which got dropped as part of the recent outage. I'm ignoring that as a one time event.

### Evidence

1. This merge: https://openlibrary.org/recentchanges/2022/12/31/merge-authors/110156479
didn't result in the works showing up in this author's record: https://openlibrary.org/authors/OL2274627A

2. This merge: https://openlibrary.org/recentchanges/2022/12/31/merge-authors/110153037
didn't result in the works showing up under this author's record: https://openlibrary.org/authors/OL2197410A

Because of the way the works list is constructed for the author's page, this basically means the works have disappeared forever (or until a complete reindex is done).

### Proposal & Constraints

### Related files

### Stakeholders
@cdrini