Actually I specified that the sizzle noise came from the USB C port, not from the charger.
What bugs me too is that Cube did not think of adding a LED to display the battery status, whereas its lifetime is decreased if you keep charging it while powered on.
Also the current known problem with the charging switching on and off may be related to this topic, even if Qualcomm officials says there is no problem. Sounds like simple PR damage control to me based on irrelevant logic as “No report ? No problem then!” :
http://www.androidcentral.com/qualcomm-addresses-usb-type-c-and-quick-charge-30-compatibility