Attachments not linked to card - files are still there

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Describe the bug

I found out today that several cards that had attachments are now missing them. One card even shows them in the Android App, but I see only a placeholder thumbnail (all are images).

In the history of each card, I see that I added the attachment, but when I click on the filename, I get a JSON with content {"status":403,"message":"Permission denied"}.

The files that were originally attached are however still in Nextcloud, i.e., in the Deck folder.

I have no idea when this happened - it must have been an update in the past 6 Months though.

Other cards still have attachments - I haven't checked all my cards though, thus I'm not even sure what the pattern is.
My only suspicion is, that these are all files I have uploaded via the Deck Android App - but I'm not 100% sure about that.

I checked the oc_deck_attachment table, and I cannot see the files there.

Is there anything else I can check? I might be able to recover backups from some months ago and could check the database there, but that would take some time.
Would it be possible to go through the history of all cards (where is this stored though?), check if files were attached, then check if these files are still in nextcloud and re-attach them?

To Reproduce
Steps to reproduce the behavior:

1. Create a card, add attachments
2. ??? - sorry, cannot reproduce :(

Expected behavior
Attachments should not be removed from card

Client details:
Independent of Client

Login as admin user into your Nextcloud and access
http://example.com/index.php/settings/integrity/failed
paste the results here.

If you have access to your command line run e.g.:
sudo -u www-data php occ app:list
from within your Nextcloud installation folder

If you have access to your command line run e.g.:
sudo -u www-data php occ config:list system
from within your Nextcloud installation folder

or

Insert your config.php content here
Make sure to remove all sensitive content such as passwords. (e.g. database password, passwordsalt, secret, smtp password, …)

Insert your Nextcloud log here

Insert your browser log here, this could for example include:

a) The javascript console log
b) The network log
c) ...

Start by inspecting the oc_deck_attachment table and the card history to determine how attachments uploaded through the Android app became unlinked while remaining in the Deck folder. Compare affected and unaffected cards, then verify that attachment associations persist and that existing files can still be opened after the fix.