I recently upgraded to Mach4 and ESS. I think I have most of the problems worked out.
The problem I have now is with threading. I didnt have a problem with Mach3. Now with M4 when I use the threading built into Mach4 turn cycles the machine starts and goes to the starting point where it waits for the index pulse. Once in a while it works. Alot of times it just sits and waits. When I hit the stop button and reset and try again usually nothing happens. Sometimes I have shut down Mach4 and restarted and it will work.
The rpm is seeing the index pulse fine, and rpm works all the time. When I run ESS diagnostic it shows the pulse flashing good. When I use the Mach diagnostics screen the index led never flashes at all but the rpm works. 
I have asked Mach about this but have not gotten an answer yet.
Does anyone got any ideas on why this is happening? I even loaded the newest version and still only works sometimes.
Thank you.

Update: I did see a post that there was problems with mach build 5000 and up with the ESS. So I downgraded Mach to 4809 like it suggested. Still the same thing. Sometimes it will thread multiple times and then it will just sit there waiting. When I hit stop a lot of times I can not even get the code to restart. It just sits on the first line and does nothing except run the elapsed time. Have to close Mach and restart it.
All other mach operations that I have used are working, just threading does not.

 It sounds like its the wait for spindle.... there needs to be an accurate measurement for the spindle RPM based on encoder feedback, and then the % of spindle RPM stabilization needs to be set to something that will work.. there will always be a little bouncing of that number.. so if the % is too small, the RPM will never be obtained...