xml looks to be fine so a few questions.
When you are getting the steady 177RPM showing do you think that is wrong?
You said you stop the spindle manually but it still reads 50 to 100, by manually are you meaning you just shut off the spindle and not tell Mach its off?
If so then that is likely why you are still getting the readings, likely two things, first Mach is still searching for a pulse as you have Not told it not to and also averaging may make the readings more persistent.
You say you dont get a spindle speed reading in cycle mode, can you explain that? What I should say is you have to tell Mach the spindle is on or it wont look for the spindle speed, whether that is via the button in Mach for spindle or whether it is via M3/M4 it doesnt matter but you must use one.
Hood