Hi durbs,
I think K2CNC is probably using PWMs to drive their bridge drivers for your servo motors. KFLOP only has one Prescaler to set the frequency for all 8 PWM channels. The bridge drivers probably need a high frequency such as 20KHz to work properly (and above our hearing range). When you change the frequency to 1KHz they have problems.
You might want to get a different module that can accept Step/Dir signals and use a spare Step/Dir output.
Or figure out how to get the K2CNC converter you have to work.
HTH
Regards