Hi msfujino,
Thanks a lot for your message and great idea.
Actually it worked to resolve the Write timeout for me. I tried on one board (I currently only have acess to 1 stucked board).
I was able to reconnect to the board (platformIO, and upload code correctly, and run it again. This is unexpected to me, because I thought the problem was on the board.
for others, here I gather all other possible solutions based on related topics:
Thanks again @msfujino for providing your answer !
The remaining question is what cause a board to get stuck after some hours running ?
Is there anything to check, or do to prevent from happening ?