Moodle 2.5 is also very old and unsupported now, so an upgrade would be wise. These issues are resolved in later versions.
We also run NewRelic and this will pick up on issues such as these that may not be showing in local logs due to the log level configured. From a developers perspective it's important to see minor problems and warnings such as these as they may be the cause of bugs or issues in the code or poor code form.