Indexing "errors" after py3 update

While doing a clear and rebuild of the catalog after py3 migration I get those log messages.
Does anyone recognise these messages?

2019-09-10 15:11:16,446 INFO    [Plone:527][waitress] Catalog Rebuilt
Total time: 14.005563735961914
Total CPU time: 13.283491999999995
Syntax Error (936): insufficient arguments for Marked Content
Syntax Error (168): insufficient arguments for Marked Content
Syntax Error (2547): insufficient arguments for Marked Content
Syntax Error (2620): insufficient arguments for Marked Content
Syntax Error (166): insufficient arguments for Marked Content
Syntax Error (2627): insufficient arguments for Marked Content
Syntax Error (171): insufficient arguments for Marked Content
Syntax Error (2540): insufficient arguments for Marked Content
Syntax Error (169): insufficient arguments for Marked Content
Syntax Error (2396): insufficient arguments for Marked Content
Syntax Error (2664): insufficient arguments for Marked Content
Syntax Error (2441): insufficient arguments for Marked Content
Syntax Error (2576): insufficient arguments for Marked Content
Syntax Error (2498): insufficient arguments for Marked Content
Syntax Error (2697): insufficient arguments for Marked Content
Syntax Error (2552): insufficient arguments for Marked Content
Syntax Error (170): insufficient arguments for Marked Content
Syntax Error (2633): insufficient arguments for Marked Content
Syntax Error (2565): insufficient arguments for Marked Content
Syntax Error (165): insufficient arguments for Marked Content
Syntax Error (2401): insufficient arguments for Marked Content
Syntax Error (172): insufficient arguments for Marked Content
Syntax Error (2533): insufficient arguments for Marked Content
Syntax Error (2358): insufficient arguments for Marked Content
Syntax Error (174): insufficient arguments for Marked Content
Syntax Error (2404): insufficient arguments for Marked Content
Syntax Error (2373): insufficient arguments for Marked Content
Syntax Error (2343): insufficient arguments for Marked Content
Syntax Error (2734): insufficient arguments for Marked Content
Syntax Error (173): insufficient arguments for Marked Content
Syntax Error (2960): insufficient arguments for Marked Content
Syntax Error (167): insufficient arguments for Marked Content
Syntax Error (2600): insufficient arguments for Marked Content
Syntax Error (2460): insufficient arguments for Marked Content
Syntax Error (2573): insufficient arguments for Marked Content
Syntax Error (2357): insufficient arguments for Marked Content
Syntax Error (2671): insufficient arguments for Marked Content
Syntax Error (2487): insufficient arguments for Marked Content
Syntax Error (2172): insufficient arguments for Marked Content
Syntax Error (2284): insufficient arguments for Marked Content
Syntax Error (2617): insufficient arguments for Marked Content
Syntax Error (158): insufficient arguments for Marked Content
Syntax Error (817): insufficient arguments for Marked Content
Syntax Warning: May not be a PDF file (continuing anyway)
Syntax Error (2): Illegal character <68> in hex string
Syntax Error: Couldn't find trailer dictionary
Syntax Error: Couldn't read xref table
Syntax Warning: Invalid Font Weight
Syntax Warning: Invalid number of shared object groups
Syntax Warning: Could not parse ligature component "warning" of "warning_sign" in parseCharName
Syntax Warning: Could not parse ligature component "sign" of "warning_sign" in parseCharName
Syntax Warning: Could not parse ligature component "external" of "external_link" in parseCharName
Syntax Warning: Could not parse ligature component "link" of "external_link" in parseCharName
Syntax Warning: Could not parse ligature component "remove" of "remove_sign" in parseCharName
Syntax Warning: Could not parse ligature component "sign" of "remove_sign" in parseCharName
Syntax Warning: Could not parse ligature component "ok" of "ok_sign" in parseCharName
Syntax Warning: Could not parse ligature component "sign" of "ok_sign" in parseCharName
Syntax Warning: Could not parse ligature component "folder" of "folder_open_alt" in parseCharName
Syntax Warning: Could not parse ligature component "open" of "folder_open_alt" in parseCharName
Syntax Warning: Could not parse ligature component "alt" of "folder_open_alt" in parseCharName
Syntax Warning: Could not parse ligature component "comments" of "comments_alt" in parseCharName
Syntax Warning: Could not parse ligature component "alt" of "comments_alt" in parseCharName
Syntax Error: Expected the default config, but wasn't able to find it, or it isn't a Dictionary
Syntax Warning: Invalid least number of objects reading page offset hints table
Syntax Error (409736): Unknown operator '<ad>+'
Internal Error (409736): Got 'EI' operator
Syntax Warning: Invalid least number of objects reading page offset hints table
Syntax Warning: Invalid least number of objects reading page offset hints table

Isn't that coming from some external converter (for PDF)?

That's also my suspicion... but didn't get far with grep and search...
Not sure what to do about it besides ignoring :wink:

Any library update necessary or similar?

Syntax Warning: May not be a PDF file (continuing anyway) may indicate a broken migration of File/PDFs?

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