=== stability across 6 healthy captures: h1, h2, h3, h4, h5, h6 ===
  T142   VARIES   Wait(XEvent)  |  --  |  Wait(XEvent)  |  Wait(XEvent)  |  Wait(XEvent)  |  Wait(XEvent)
  T141   VARIES   --  |  Wait(XEvent)  |  Wait(XEvent)  |  Wait(XEvent)  |  Wait(XEvent)  |  Wait(XEvent)
  T140   VARIES   --  |  Wait(XEvent)  |  Wait(XEvent)  |  Wait(XEvent)  |  Wait(XEvent)  |  Wait(XEvent)
  T139   VARIES   --  |  Wait(XEvent)  |  --  |  --  |  --  |  --
  T133   STABLE   Wait(XEvent)
  T132   VARIES   Wait(XEvent)  |  --  |  Wait(XEvent)  |  Wait(XEvent)  |  Wait(XEvent)  |  Wait(XEvent)
  T80    STABLE   WaitMultiple(XEvent,XSemaphore)
  T79    STABLE   WaitMultiple(XEvent,XSemaphore)
  T78    VARIES   WaitMultiple(XEvent,XSemaphore)  |  Wait()  |  WaitMultiple(XEvent,XSemaphore)  |  WaitMultiple(XEvent,XSemaphore)  |  WaitMultiple(XEvent,XSemaphore)  |  WaitMultiple(XEvent,XSemaphore)
  T77    STABLE   Wait(XEvent)
  T76    STABLE   WaitMultiple(XEvent,XTimer)
  T75    VARIES   Wait(XSemaphore)  |  --  |  Wait(XEvent)  |  Wait(XEvent)  |  Wait(XEvent)  |  Wait(XEvent)
  T74    VARIES   Wait(XSemaphore)  |  --  |  Wait(XEvent)  |  Wait(XEvent)  |  Wait(XEvent)  |  Wait(XEvent)
  T71    STABLE   Wait(XEvent)
  T69    VARIES   --  |  --  |  --  |  Wait(XSemaphore)  |  --  |  Wait(XSemaphore)
  T68    VARIES   --  |  --  |  --  |  Wait(XEvent)  |  --  |  Wait(XEvent)
  T67    VARIES   --  |  --  |  Wait(XEvent)  |  Wait(XEvent)  |  Wait(XEvent)  |  Wait(XEvent)
  T66    STABLE   Wait(XEvent)
  T65    STABLE   WaitMultiple(XEvent,XSemaphore)
  T64    STABLE   WaitMultiple(XEvent,XSemaphore)
  T63    STABLE   Wait(XSemaphore)
  T62    STABLE   Wait(XEvent)
  T61    STABLE   Wait(XEvent)
  T50    VARIES   --  |  --  |  Wait(XEvent)  |  Wait(XEvent)  |  Wait(XEvent)  |  Wait(XEvent)
  T36    VARIES   WaitMultiple(XEvent,XEvent)  |  WaitMultiple(XEvent,XEvent)  |  WaitMultiple(XEvent,XEvent)  |  --  |  WaitMultiple(XEvent,XEvent)  |  --
  --- 12 stable, 13 vary across healthy play
  Only a thread in the STABLE set can carry a frozen-state signature;
  a VARIES thread differing when frozen proves nothing.