Running the current 0.4 release of Reality Check on Linux leads to completely erratic and seemingly random results.
This is being caused by os.clock() which returns non-realtime process-specific time values and thus cannot be used. socket.gettime() should be used as a replacement.
Branch realitycheck_linux already contains a fix but the change has not yet been tested under Windows. An update should be released if it is confirmed to work as expected on Windows as well (otherwise Windows should continue to use os.clock() which apparently has been sufficiently accurate so far).