Error in offline use of nextcloud files in an application over SAF

On my android phone I use KeepassDX with the database file on Nextcloud provided via SAF.

In the Nextcloud mobile app I have selected the “Download” option on the keepass.kdbx file, and it has the green checkmark icon. In KeepassDX I can see the file it uses is content://org.nextcloud.documents/document/330180472/7 - I assume this is the SAF url(?).

The problem is that when I’m offline, I can’t open the keepass database. The error I get is:
Could not load your database. Error downloading file….

I’m not sure if the error is in how KeepassDX uses SAF or something in the nextcloud mobile app. Any pointers how to debug this further?

phone is Android 11, Pixel 4
Nextcloud android app is 3.15.1
server is Nextcloud 21.0.1 (self-hosted)