On one of the forums there was s thought that I'm getting overvoltage due to the regenerative energy when I slow or stop my motors. This buck can't sink current, and even if it could it may pump up the input cap until the IC fails.
Crap.
It fails because the layout is poor. I have never seen a professional power supply engineer that could make a good layout first time, normally two or three iterations are needed. They work fine with low current but can oscillate with the full output voltage at specific currents. This could also be just at some value of high current.
Which modules are crap? All of them I've chosen according to the supplier's calculation file.
All the cheap ones on eBay are crap. Suppliers there lie, and are deliberately obscure. A favourite trick is to give a voltage rating and a current rating which the module can reach, but they neglect to say it is not at the same time.