Hi, thanks for posting!

As the tests are exhibiting inconsistent pass/fail results in NCrunch, I would strongly suspect one of the following:

1. The tests are sequence dependent. They perhaps depend upon being the first test executed inside the test run, or perhaps on another test being run before them inside the same process
2. The tests contain race conditions (i.e. multithreaded code) causing their results to be inconsistent

I recommend having a good look through the tests and the code they execute to see if there is a common pattern between them.

It's worth having a read of the following two documentation pages, as they may help give you a better understanding of the differences between NCrunch and other test runners when dealing with these tests:

http://www.ncrunch.net/documentation/considerations-and-constraints_test-atomicity
http://www.ncrunch.net/documentation/troubleshooting_test-and-runtime-related-issues

Are you able to make the tests pass artificially in NCrunch consistently?

Does this happen when you try to debug the tests using NCrunch? If so, does the debugger pick up the exception that would result in the test failing?

Are you able to supply code or steps to reproduce the issue?