Hi there,
SourGrapes…
Ignore the Whiner in this thread, Even if your stuck in a boot loop and can’t get it to go, try this, It works in all situations BUT you have to have the necessary Hand , Eye coordination to pull it off.
Hilarious, Guy sends BAD code to it and Nerfs it up , then blames hardware. when the problem really exist between the Keyboard and the Floor. 
" compile a blinky example as normal, verify its a good compile. "
Unplug Xiao, Press Upload and if you time it right “reconnect Xiao as it gets to the actual upload portion”
Takes a few tries , but if you get it just right it will hook and upload, thus “UN-Nerfing” the KaKa 
code you sent previously.
Works every time I wack a bootloader or write out of memory bounds in my experimental code.
HTH
GL 
PJ
A whiner is someone who complains a lot, especially in a self-pitying or peevish manner or tone. Whiners often complain about little things, and can also be described as disagreeable or unpleasant people 