I've encountered a frustrating roadblock in few distance debugging situations recently, and I have looking for a term to describe the problem. Here's the issue, in a nutshell:

A sticky problem on a remote system has been narrowed down to a likely cause, such as the interaction of two different applications. A test has been proposed to verify this assessment, which is to remove one of the applications, and run the test procedure again. However, the remote resource balks, saying "But we'll need both of those applications on the real system!" The problem is that they have conflated testing and fixing. In other words, they have taken the suggestion of "remove an application to test the theory" as "remove the application to fix the problem", when one does not have to imply the other.  Unfortunately, with these issues mixed together it creates a mental roadblock where you can no longer make headway by ruling a particular cause in or out.

So what can be done? I've found that the first thing to do is make the test/fix separation explicit. Tell the remote resource, "I understand that this is a not a permanent solution, but until we've verified that the application interaction is the problem, there is no point in pursuing other solutions." Another tactic is to offer a test procedure that involves undoing and then redoing the piece that your remote resource insists is untouchable to address their fears.  In the conflicting applications example, this might be, "Remove one of the applications and check to see if the problem still occurs.  Then reinstall that application and try it again to verify that the problem is back again."  Finally, make it clear that you understand the constraints by saying things like, "I know that you will need both applications in the long run.  I'm sure that once we've narrowed it down, we can find out what the conflict is and resolve it."  Once you have shown your focus on getting to the cause rather than proposing a solution, your remote resource should be more receptive to allowing you to try something out.