The threshold packages have to be manually modified when you want to add new packages, or tune the parameters of an existing package. The reason for this is because there is no WebUI to manage changes on this file.
If the operator introduces an error on this file and send the reload event for it, Collectd will stop gathering data until the error is fixed.
If there is an error on the file, the current configuration in memory should be used until the error is fixed, and this should not block the operation of Collectd.
After fixing the file, you have to restart OpenNMS.
I verified this behavior on my test environment running latest foundation-2016.
Also, this kind of errors can be detected if the files can be verified: