I can't explain it.
For some people the device works without problems, for others it doesn't.
What could be the reason for this? Has the design of some devices been changed, different chips used or something similar?
Agreed. I've posted here before, and wonder a lot about why it be so very different from user to user?
(For instance what is the point of having a high setting when it only works on, let' say... 1-5% of all devices? What is the reason for it NOT working on high for the rest of us?)