My home server’s backup script suddenly stopped running overnight—no errors, just silent

I set up a Raspberry Pi as a home server to run nightly backups of my family photos and documents to an external HDD. It’s been working flawlessly for months with a simple cron job that triggers a bash script at 2am. But starting last week, the backups just don’t run anymore. The script itself hasn’t changed, and there are no error logs or email notifications from cron. I’ve checked that the Pi is powered on and connected to the network each morning, and manually running the script works fine. I’m guessing something might have changed with the cron environment or permissions, but I haven’t touched any system configs. I also tried replacing the cron job with a systemd timer, but it behaves the same. Has anyone experienced this kind of silent failure with cron jobs on Raspberry Pi OS? What’s the best way to debug or log these kinds of background tasks that suddenly stop without any visible errors?