I've tried with turn diags enabled
The turn diagnostics should not be used in version .032 and above, so un-enable the plug-in.
Like Hood replied, you need to turn the spindle on as that tells Mach to imeadiately start looking for the true rpm from an index pulse.
Make sure you do not have timing enabled. It dosen't work after .032 and is not better than a single index. The thread changes were implemented in 3.042.032 and .033 took care of a negative dro rpm problem for computers with a fast bus speed.
I use 10 for the index debounce and 600 for the interval. You may need to set yours to something different.
RICH