After the update to 5.800 my phone reported a K-9 gmail authentication error on July 28 and July 31, followed shortly by an email from Google with the subject “Critical security alert”
“Sign-in attempt was blocked - Someone just used your password to try to sign in to your account. Google blocked them, but you should check what happened.”
myaccount.google.com: Suspicious sign-in attempt prevented.
Google prevented someone who knows your password from signing in to your account. If this wasn’t you, you should change your password immediately.
followed by: Unknown device Germany (this could be significant because the device IS known.
FYI: This occured both times on a Samsung Phone with Android 9 while on mobile data, in the meanwhile the K-9 has been updated to 5.801