Search index access failure events

Event Viewer lists 14,737 warning events stating:

The content source <ONEINDEX14://{S-1-5-.....}/> cannot be accessed **

Context: Windows Application, SystemIndex Catalog

Details:
(HRESULT : 0x80004005) (0x80004005)

**(.....denotes some text deleted)

These events date back to just a few days after I installed an SSD. This is significant because at that time, I created a 'Scratch' partition on a mechanical drive to accommodate system temp files, etc. This included the search index.

I've noticed that indexing has been a bit quirky, but only now looked into it. Indexing Options|shows just under 300, 000 files are indexed. I guess that's about right, since Everything Search lists just over 400,000.

Any ideas on how to correct the index access issues?

Thanks!

Edit: After researching, I've deleted the SID in the Registry key noted above (<ONEINDEX14:... ) and am rebuilding the index. I'll post back after enough time has passed to verify the error has or has not continued.

For anyone else who comes across this by google,

Here is the tutorial for rebuilding search index.

Index - Rebuild