I have same problem here
My scooter project (brushed 36v/1000w)
I bought this pwm controller and fried it with some tests.
Then I bought a bigger pwm controller like the one you using, but still without success to drive it from Arduino.
First I plug the scooter throttle (same of e-bikes) to my Arduino Uno, read the parameters in analog pin and convert to 0-255 analog write.
Tested with a multimeter and with some adjusts it works great: outs 0 to 5v "correctly"
Then I took 3 1,5v batteries in series (4,5v) and tested on pwm controller: With default connections (36v batteries connected, motor connected and default potenciometer connect and running on middle velocity I pluged the negative of 4,5v batteries on red of potenciometer and softly put the positive on the middle pin of potenciometer. It increases the motor rotation, indicating it works.
Then I replace the 4,5v batteries connections to GND and analog +5v of my Arduino. And fried it on moment I plug. Goodbye to my Uno.
Now I have no ideas what to do. When I plug the throttle replacing the potenciometer (just pluging same pins) the motor wont be on zero. I thing the throttle sends from 0,8 to 5v... so my scooter never stops...