Resharper unit test sessions changing test results to unknown after build

I am running a suite of NUnit tests using the Unit Test Explorer/Sessions window in Resharper Ultimate 9.2 and Visual Studio Enterprise 2015. I start a new test session from the unit test explorer every night with the tests that I want to run and run all of them from within the unit test sessions window after renaming the new session to include the current date. Most of the time the results are remembered with no trouble and I can work through the results and debug the ones which failed, but sometimes after building all of my test results in all sessions will get marked with "unknown" result status.

This doesn't always happen and it seems to happen more often if I merge lots of code changes in from a different TFS branch.

Is there any way to force resharper not to mark the tests as unknown and retain all the results that I had? I know that I can export the results to XML (and do now, for this very reason) but it's harder to read and navigate the results in an XML file than the Resharper unit test sessions window, so I'd lilke to do that if possible.