Above are photos of a couple of DC-DC voltage step down modules using a LM2596S.
Both are rated at 3A with 3v - 35v input, and 1.3v - 34v output.
One of them has what looks to me like a possible problem?
There are probably more than one possible problem with these modules.
Your mission, if you choose to accept it, is to spot the possible problem, and tell me if you think it would a reason not to buy that particular module.