False error importing term set into site level term store

I have a CSV file that I'm using to create a term set in a site (NOT in the tenant, just a site). The file has 122 rows, including the header row. Upon importing the file, I get this error message:

Not all terms were imported successfully. Please see the server log for more information.

According to this page: https://learn.microsoft.com/en-us/sharepoint/troubleshoot/search/troubleshoot-error-when-importing-a-term-set, this error occurs when importing more than 5,000 terms. However, the file I'm using doesn't have nearly that many. Also, looking through the imported terms, there don't seem to be any missing. I've also opened the CSV in a plain text editor (Notepad++) to ensure it didn't have a bunch of empty rows that may have been seen as part of the import.

Is this just a bug when importing at the site level? Incidentally, I ran an import with about half of the terms (as a "proof of concept" and to be sure I had the hierarchy right) yesterday and did not get the same error.