"Maintain original filename" isn't working for old photos uploaded

Steps to reproduce

1. Go into "More" -> "Settings" -> "Auto upload" and enable "Auto upload photos/videos"
2. Scroll down to the bottom and go into "Change filename mask" Make sure "Maintain original filename" is selected
3. Go back up to "Auto upload" and enable "Upload the whole camera roll"
4. Wait for some photos to upload

Expected behaviour

The photos that are uploaded should keep the filenames they have on the phone. The normal format should be
IMG_5468.JPG but if the files have other filenames originally those should also be respected.

Actual behaviour

All old files being uploaded are named something similar to A312123E-52D5-418E-24CF-52C4D132616B.JPG.

Any new photos that I take that are uploaded is named on the expected format, IMG_5468.JPG

Screenshots

Logs

Reasoning or why should it be changed/implemented?

Environment data

iOS version: e.g. iOS 15.3

**Nextcloud iOS app version: 4.2.1.7

Server operating system: Docker

Web server: Apache

Database: Postgres

PHP version: 8.0.15

Nextcloud version: 23.0.1

No source file or test is named. Start by reproducing the issue through Auto upload, Change filename mask, and Upload the whole camera roll, then trace how the selected filename mask is applied to existing versus newly captured photos. Done means old photos retain their original phone filenames while new uploads keep their current naming behavior.