When converting certain outlined PDFs to PDF/X using the Preflight tool, in the resulting PDF many characters are missing (already on screen, before printing). This makes the Preflight tool unusable.

1. Open cmyk-14-input.pdf
2. Use print production -> Preflight -> PDF/X -> Convert to PDF/X-4 (Coated FOGRA39) or any other of the PDF/X profiles or use the "Standards" tab with "Apply corrections" checkbox enabled.
3. The resulting PDF is completely destroyed (see cmyk-14-output_audit.pdf)

Environment: Windows 10, Adobe Acrobat 23.1.20174.0
Expected result: An output visually similar to the input cmyk-14-input.pdf
Observed result: A garbled output like cmyk-14-output_audit.pdf

Some observations:
* This does only happen with outlined text, not embedded/subset fonts.
* This happens regardless of whether the input document is in RGB (see rgb*.pdf), CMYK or already adheres to some PDF/X standard.
* This does not seem to happen on the last page, i.e. one-page-documents are fine.
* With the other pages, something seems to go wrong with the colorspaces of the individual pages.
* This does not happen if the "Convert Color" fixup is manually disabled (Edit profile -> Summary -> Create customizable profile -> Custom fixups -> untick checkbox "Enable fixup" for "Convert colors" (see result cmyk-14-output-no-convert-coloraudit.pdf). This is even weirder since this also helps for CMYK/FOGRA39L documents, where the Convert colors fixup is allegedly not even executed (according to the list of applied fixups in the Results view, see cmyk-14-outputreport.pdf).

Thank you in advance.