Indexing Fails When Configuring Smart Search

I am trying to enable smart search on a particular record type, but I keep getting "Indexing failed" errors. I'm new to this feature, so I'm not really sure where a good place to start troubleshooting is, but I've listed what I've done/noticed below and attached a screenshot of the error.

• I have successfully set up smart search on 2 other record types in the same environment
• A difference between the 2 records successfully using smart search and the one that is failing, is the primary key of the failing record is type text and can contain some symbols (periods and hyphens mostly) while the other 2 are type integer. Not sure if that's relevant or not.
• When performing a full sync on the record, the "total record type rows" shows that it has 2 more rows than the "total source rows", but when viewing the record list the row count is correct.
• I've tried changing the fields that smart search uses with no effect

If anyone has some other ideas of what might be causing this, what I can try, or could point me to the log where I could get some more details, that would be greatly appreciated!

Thanks,

Jack