LM2596 Step-Down Power Module issue

I have a number of small electronics projects that I've been wanting to work on. It is something I definitely have had mixed success with. However, a small thing I learned today about the LM2596 Step-Down Power Module.

I originally bought this module to power a project for my own self built sprinkler controller system. After melting one or two of these modules I realised that this module is DC-DC when I needed an AC-DC version for that project. However, I had tried a few times to get this particular module to work and had no luck - it seemed like turning the potentiometer on top would just not adjust the voltage and the display did not change.

The lesson learned today - just keep turning.

There appears to be a threshold for quite a while where it does not adjust anything, then it'll suddenly jump and move very quickly to the desired output voltage. In frustration I had opened up the second one I had, fresh out of the packet and saw the same issue I had with the first.