one sunny day on Debian8.7
as a result of this action:

i got the stated error message:

/usr/bin/xauth:  timeout in locking authority file /home/user/.Xauthority

root@debian:/home/user# ls -lah|grep ICE
-rwxrwxrwx  1 user user 4.7K May 10 16:25 .ICEauthority # chmod ugo+rwx did not help

# the problem is the home directory is owned by root :-D
# because of the chroot sftp "user do not escape home" thingy of the above link

ls -lah /home
total 12K
drwxr-xr-x  3 root root 4.0K Apr 24 14:11 .
drwxr-xr-x 22 root root 4.0K May 11 09:50 ..
drwxr-xr-x 25 root root 4.0K May 11 09:52 user

# per default user rights are like this:
# the user user has it's own group users and completely owns this directory
/home$ ll
total 4.0K
drwxr-xr-x 24 user user 4.0K May 11 10:05 user

# fixed the problem
# 1. make root own all user directories
# 2. but at the same time give the user's own group write access to user's home directory

root@debian:~# chown root:user /home/user
root@debian:~# chmod g+w /home/user


so what was the problem?

The user had no write access to his home directory could not create new files via touch 1 2 3

hence the error.

rebooted and gnome2 session started normally.