Not seeing that problem here so far when using your xml. I am poresuming it is the DROs in Mach and the tool display as well as your motors that are slowing down?
What is the frequency showing on Diagnostics page and also what is Time in Int, also check CPU usage and see if its loading up, especially when things slow down.
Hood
CPU is ok but the pulse frequency when running OK is 25,387 but slows to 100 when everything slows. Yes it is the DRO's and the tool display as well as the motors.
Thanks for your help Hood.