SQLite DB won't update when running PHP script from cron

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I cannot update a SQLite DB when running the PHP script from my crontab.

When I just open example.com/app.php in my browser, it works fine. Same when I run

php -q /opt/bitnami/apache2/htdocs/app.php 

But my crontab

*/5 * * * * php -q /opt/bitnami/apache2/htdocs/app.php >> /opt/bitnami/apache2/htdocs/log/monitor.log 2>&1

won't update the SQLite DB. I have implemented a file log (at the end of my file) as well, and it gets written every run. So the crontab runs and seems to be working. The cron log is empty.

I have verified that SQLite is enabled with:

php -a if(class_exists('SQLite3')) echo 'ok';

The directory and the DB file itself are both rwxrwxrwx.

Any ideas? Why is it working, running the script directly from CLI but not from within the crontab? The only difference should be the user, but permissions are set to 777. So I cannot see where the problem is.

Server is AWS Lightsail with PHP 7.3

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EDIT: Crontab is of user bitnami