Code coverage at 0%, only for some files

We have about 86% code coverage on 9K lines of C# code.
But it has been dropping lately and we are looking to increase it.
Some files have 0% on code that I know is called from the tests.
Even constructors that are called directly by the tests in the arrange steps.
How do I debug this?

Sonar, Version 6.7.7 (build 38951)

<executable>C:\Program Files (x86)\Microsoft Visual Studio 12.0\Team Tools\Dynamic Code Coverage Tools\CodeCoverage.exe</executable>
	<arguments>
		<argument>collect</argument>
		<argument>/output:cc.coverage</argument>
		<argument>C:\Program Files (x86)\Microsoft Visual Studio 12.0\Common7\IDE\CommonExtensions\Microsoft\TestWindow\vstest.console.exe</argument> 
		<argument>SUT.dll</argument>
		<argument>/Logger:trx</argument>
	</arguments>

hi @bwhite

we recently discovered ourselves this issue on our own project, see https://github.com/SonarSource/sonar-dotnet/issues/3191

could you provide a reproducer project? it would help us investigate

also, could you please update the SonarCSharp version to the latest, in order to be able to get improved logging for code coverage reporting

to debug the coverage importing, after you’ve updated SonarCSharp from the Marketplace to the latest version, please add /d:sonar.verbose=true to the BEGIN step and then attach the output of END step