@Danny Danny. Before I get into my long sad story with Banggood, I’ll direct you here:
In that thread, Paul shows that you do not need an oscilloscope to determine if the pwm controller on the longmill board is behaving. I followed it and found that mine was.
You should also read this thread:
Once I followed Paul’s advice and saw that my LM controller was fine, I had to conclude the laser was defective. I’ve already set out the steps that I had to go through to get Banggood to replace it. It was not fun. I will never deal with them again. I did finally get a replacement, though.