App losing DB credentials

I installed an application based on Dancer using the Dancer::Plugin::Database module at the beginning of the week and notice that the connection to the mysql DB got lost after a few days of running.

Logs report crashed: DBI connect('database=xxxxx','xxxxx',...) failed: Access denied for user 'xxx'@'localhost' (using password: YES)

The authentication method is user/password and they are of course correct. Mysql was fine at the time the application was crashing and I could connect with mysql client using the application credentials.
Restarting the application solved the problem.
The application is deployed with plask:
sudo -u www-data /usr/local/bin/plackup -E production -s Starman --workers=1 -l /tmp/plack.sock -a bin/app.pl &
I am using the Dancer::Plugin::Database plugin with connection_check_threshold: 10

What could cause an access denied ? According to mysql doc, this message means wrong password. Could the in-memory password just get lost ? Weird.