[Bug]: 'PDF conversion' flow does not properly update PDF

⚠️ This issue respects the following points: ⚠️

• This is a bug, not a question or a configuration/webserver/proxy issue.
• This issue is not already reported on Github OR Nextcloud Community Forum (I've searched it).
• Nextcloud Server is up to date. See Maintenance and Release Schedule for supported versions.
• I agree to follow Nextcloud's Code of Conduct.

Bug description

All latest as of this day versions

Nextcloud 31.0.2
'NextCloud office' app 8.6.4
'Collaborative tags' app 1.21.1
'Workflow external scripts' app 2.0.0
'Automated PDF conversion' app 2.0.0 (LibreOffice installed on the server)
'PDF viewer' app 4.0.0
Manual changes to files in https://github.com/nextcloud/server/pull/51927
Collabora Online server (NOT built-in CODE)
NextCloud Encryption enabled

Problem: PDF not correctly updated in 'overwrite existing PDF' mode with 'PDF conversion' flow.

1. Created flow for PDF creation/update upon 'file created' and 'file updated' events with the following settings

Note - event type does not matter here, the error is reproduced with other trigger events (except for 'tag assigned', which does not work anyway - see https://github.com/nextcloud/server/issues/51849 )

2. Created ODT file with content 'Lorem ipsum'

3. Cron job executed. PDF is generated by the flow, with 'Lorem ipsum' content.

4. Modified ODT (added 'Mod'), saved changes

5. Cron job executed. PDF file was somehow changed, but there are NO visible changes to the content, the original 'Lorem ipsum' is still there

If PDF is downloaded, it also 'Lorem ipsum' version.

6. Then, on PDF file, going to Open Details > Versions > clicking on 'Initial version' or 'Current version' or 'Compare to current version' nothing happens - black screen, infinite loader

6. Then, on PDF file, going to Open Details > Versions > 'Current version' - Download. Downloaded version is 'MOD Lorem ipsum'

So somehow PDF is updated inside, but not written properly (cache, DB, etc, no idea), so end-user still sees old PDFs, when PDF is accessed from regular UIs.

Reproduce the reported sequence using the PDF conversion flow, cron job, overwrite-existing-PDF mode, and Versions UI described in the issue, with the listed Nextcloud and app versions. Review the manual file changes associated with PR #51927 and compare the generated PDF's visible content, downloaded content, and version actions; done means updated PDFs are shown and the Versions actions load correctly.