In the named test, the call to checkContainsWithCountJson is too permissive. Prior to the failure point in the jsTest, every query is mirrored. This means that multiple log statements with mirrored: true can show up in the time between running a command and checking on the logs. Since the call to checkContainsWithCountJson checks for only one instance, this test will fail when more than one line with mirrored: true shows up.

The solution here is to append all of the commands in the file with a comment, and then add that comment to the filter logic for the call to checkContainsWithCountJson.