Just out of desperation, I’ve reflashed the whole module (including tinybooter). Now it kind of works.
That totally freaks me out.
Not sure why it is!
Please share with us if you have any news from this!
Yeah I do not like this, too 
It looks like sometimes it just happens with G400, like https://www.ghielectronics.com/community/forum/topic?id=13621
Anyway, thanks for your help Dat, If something changes, will let you know.