TYPO3 Core

We had 2 similar TYPO3 9 installations with EXT:indexed_search search, that were configured to index pages and files (pdf, ...). All worked fine in v9, running on Mittwald Managed server with the necessary tools to index PDFs. Several PDFs got indexed and could be found in the search in frontend.

Now both system got upgraded to 10.4.6. and the search in frontend is still working but the results don't show any pdf files any more, using the same search words that worked in v9. Also in the backend module of EXT:indexed_search we still see the pdf files content being in the search index. No configuration was changed, no php or mysql version changed, hosting is the same, no extensions got added or removed on the upgrade.

Is the indexing and / or searching of external files in EXT:indexed_search currently broken in v10?