launchd script file access blocked by sandboxd

I've written a small shell script that downloads some server data and saves them into a restic repository. The restic repository files are on a mounted volume. The script works fine if I run it in the Terminal. To run this script daily I created a launchd .plist file in ~/Library/LaunchAgents Watching the output logs, I can see that the restic command fails to access its files. The system logs show a sandboxd warning that blocked restic. I've granted Full Disk Access to the restic binary, but that didn't do the trick. What am I missing?