How can I fix this issue the correct way? As it seems to appear after a while at random times... the only way to fix is to go from 2.0.x to 2.2.x or vice versa.
Bad Request Your browser sent a request that this server could not understand. Reason: You're speaking plain HTTP to an SSL-enabled server port. Instead use the HTTPS scheme to access this URL, please. Hint: https://mysite:80/ Additionally, a 404 Not Found error was encountered while trying to use an ErrorDocument to handle the request.