It appears that the eventual high memory usage leads to authentication failures, and the following messages are logged:
/var/log/sssd/sssd_some.domain.log (Tue Oct 11 08:05:11 2016) [sssd[be[some.domain]]] [ad_account_info_complete] (0x0010): Bug: dp_error is OK on failed request /var/log/auth.log Oct 11 08:12:09 somehost pwauth: pam_sss(pwauth:auth): authentication failure; logname= uid=33 euid=0 tty= ruser= rhost= user=someuser Oct 11 08:12:09 somehost pwauth: pam_sss(pwauth:auth): received for user someuser: 4 (System error) A restart of sssd service resolves the authentication problems.
