Logon information not available (Security Event Log)

Last tuesday (April 4th, 2017) our 4 Domain Controllers (Windows 2012R2) have been updated with the latest updates from Microsoft and have been seperately rebooted. From that moment our ADAuditPlus server cannot read logon information anymore from our domain. We did not change anything regarding settings in ADAuditPlus (all 4 DC's are available and working), nor did we change anything concerning policies and/or settings on our Domain or it's controllers. There is still some information read from the DC's, but not the information it should be able to get from the Security Event Log.

Any one any idea what could possibly be wrong?