Mach3, ESS Smoothstepper, C25S BOB, Gecko G251x driver, Windows 10, The PC is connected to WIFI.

I am having a intermittent problem with lost steps, The lost steps have always coming from the Y slave driver to the left side Y stepper motor.

If I switch the cables to the steppers, (please see drawing) and send the Y slave driver output to the right side stepper, the right side stepper starts loosing steps.

This looks like it isn't the stepper motor, or the stepper coupler.

What could be the cause of loosing steps????????

I was told by a friend to run the steppers slower because I was always loosing steps, so the next day I ran the below test It ran so well until later in the test, and I realize thet 200 IPM is extreme for me.

Here is some testing I have done at different speeds.
Material 3/16" plywood, 1/8" single flute end mill, cutting 0.050" per pass, the letter outline I'm cutting is 12"x14"

Test 1 pass 60 IPM
Test 2 pass 60 IPM
Test 3 pass 75 IPM
Test 4 pass 75 IPM
Test 5 pass 100 IPM
Test 6 pass 125 IPM
Test 7 pass 150 IPM
Test 8 pass 175 IPM
Test 9 fail 200 IPM Realign gantry
Test 10 pass 75 IPM
Test 11 pass 75 IPM
Test 12 fail 75 IPM Gantry skew left 33" right 34 3/4"
Stepper temperature left 170 F right 185