No idea how to solve the main issue.
Re-entering credentials is not easy.
As the credentials window can’t be put in background.
As workaround, I send from my PC to myself the credetials minus 1 or 2 chars (security, just in case…) in some messaging app or email on the same line.
So I can copy ID and PW at the same time.
Then, I paste both in the ID and password fields and then only delete the inappropriate ones and add the missing chars.
Well, still a hassle, but less than whorse… 
Edit: does the workaround from here work for you?
(Settings → SF Utilities → restart network subsystem)