Really odd this is happening.
They have not changed motor current levels, PWM_GRAD, nor PWM_AMP in the firmware.
Nothing I can see in the firmware should have changed power draw and heat dissipation for the motors.
Are the axes free of motion resistance that would increase current demand?
Is power supply voltage on the affected printers at a lower than normal level?
What are the voltages being reported in support during printing?
If those are below 23.8, I would adjust voltage potentiometer in power supply upward.
Are EINSY power connectors secure?