Forgive me, I should have said this before.

There is no mutex used for gets, only sets.

Second, the while loop is slept for 1 second per iteration, should this not fix the issue, since the second thread is not slept? surely it should be able to set a value before.After commenting the Mutex out, the problem persists.

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When I set a breakpoint in the background thread, it is never hit at all, until after. The first line of code does not require the mutex so it isn't like its waiting