My advice is to not leave wi fii on if You don't need it.
I had a problem: I left my Home for 2 days (unusually without my Kindle) and when I come back my Papewhite (7 gen) had the battery at zero. My internet provider had a fault and the Kindle reached the wi fii but, of course, couldn't go to Amazon's server, it tried again ecc until the battery was at zero.
I tried to resuscitate my Kindle by attaching it to the power outlet but nothing. Then I called Amazon's customer service, they told me to do it again and it worked.