I downloaded the zip for cube i7 book from cube-tablet.com. It’s a 7GB zip containing win10, bios and ec files and a chinese documentation about flashing win10, bios and ec.
I translated that document. There was a note, that reflashing the ec (ec means embedded controller) might help with power or charging problems.
So it might help with your problems described here. Flash/upate BIOS might help as well.
I can post the translated doc, if you like. But be warned: I don’t speak chinese and used google translator and tried to figure out, what it should mean. But I guess, it’s pretty accurate, at least it makes sense from a techical point of view, also there are a lot of english screenshots.