I don't think the brand is very relevant, though I did hint so - sorry! Except if someone would have the exact same, but these things are so easy to design that there must be dozens of makes and models on the market.
Perhaps - as you guess - the switching regulator is crap; but it is also possible the installation is, err, less than perfect.
Last edited by Jan Olieslagers; 20th Oct 2016 at 08:19.