AD Replication: "Value does not fall within the expected range"

Hi

I have two DC's at the same site. Working fine until I recently got "Value does not fall within the expected range" on the 'Active Directory Replication Errors' sensor. No changes have been made to ether DC recently. No Windows updates were installed before this time. This sensor went into an error state between 08:40 and 08:45 - The event log on both servers shows nothing unusual around this time. Both servers have been rebooted since and the problem continues.

I have turned on logging data for this sensor and this is the output. (I have changed our domain to "domainname.co.uk" and changed the server names to "server-dc1" and "server-dc2" respectively.

Data['linuxloginpassword'].asString := '';
Data['notonpod'].asString := '0';
Data['fastcount'].asString := '0';
Data['valuetype'].asString := '0';
Data['lastmsg'].asString := 'Value does not fall within the expected range.';
Data['windowsloginusername'].asString := 'prtg.user';
Data['exefile'].asString := 'ADSReplFailuresXML.exe';
Data['hostv6'].asString := '';
Data['lastuptime'].asString := '0';
Data['writeresult'].asString := '0';
Data['blockedsens'].asString := '';
Data['reqmsginterval'].asString := '60';
Data['windowslogindomain'].asString := 'domainname.co.uk';
Data['tlsexplicit_imap'].asString := '';
Data['channelnames'].asString := 'Last Sync Result'#$D#$A + 
'2'#$D#$A + 
'Scheduled Sync Disabled'#$D#$A + 
'3'#$D#$A + 
'Is Deleted Source'#$D#$A + 
'4'#$D#$A + 
'Consecutive Sync Failures'#$D#$A + 
'5'#$D#$A + 
'Modified Consecutive Sync Failures'#$D#$A + 
'6'#$D#$A + 
'Pending Replication Operations'#$D#$A + 
'7'#$D#$A + 
'Last Sync Attempt'#$D#$A + 
'8'#$D#$A + 
'Last Sync Success'#$D#$A + 
'9'#$D#$A + 
'';
Data['tlsexplicit_default'].asString := '';
Data['canlinux'].asString := '0';
Data['isexesensor'].asString := '1';
Data['windowsloginpassword'].asString := '***';
Data['environment'].asString := '';
Data['mutexname'].asString := 'ptfadsreplfailureID2322';
Data['channelinfos'].asString := '{"2":{"Unit":"oukCount","CustomUnit":"#","ValueLookupName":"","LimitMode":"0","LimitMinError":"","LimitMinWarning":"","LimitMaxError":"","LimitMaxWarning":""},"3":{"Unit":"oukCustom","CustomUnit":"","ValueLookupName":"prtg.standardlookups.yesno.statenook","LimitMode":"0","LimitMinError":"","LimitMinWarning":"","LimitMaxError":"","LimitMaxWarning":""},"4":{"Unit":"oukCustom","CustomUnit":"","ValueLookupName":"prtg.standardlookups.yesno.statenook","LimitMode":"0","LimitMinError":"","LimitMinWarning":"","LimitMaxError":"","LimitMaxWarning":""},"5":{"Unit":"oukCount","CustomUnit":"#","ValueLookupName":"","LimitMode":"0","LimitMinError":"","LimitMinWarning":"","LimitMaxError":"","LimitMaxWarning":""},"6":{"Unit":"oukCount","CustomUnit":"#","ValueLookupName":"","LimitMode":"0","LimitMinError":"","LimitMinWarning":"","LimitMaxError":"","LimitMaxWarning":""},"7":{"Unit":"oukCount","CustomUnit":"#","ValueLookupName":"","LimitMode":"0","LimitMinError":"","LimitMinWarning":"","LimitMaxError":"","LimitMaxWarning":""},"8":{"Unit":"oukTimeSeconds","CustomUnit":"#","ValueLookupName":"","LimitMode":"0","LimitMinError":"","LimitMinWarning":"","LimitMaxError":"","LimitMaxWarning":""},"9":{"Unit":"oukTimeSeconds","CustomUnit":"#","ValueLookupName":"","LimitMode":"0","LimitMinError":"","LimitMinWarning":"","LimitMaxError":"","LimitMaxWarning":""}}';
Data['uptimecount'].asString := '0';
Data['interfacenumber'].asString := '';
Data['reboot'].asString := '43514.4131406944';
Data['usednstime'].asString := '0';
Data['linuxlogindomain'].asString := '';
Data['ptfwriteresult'].asString := '1';
Data['tlsexplicit_port'].asString := '';
Data['monitorchange'].asString := '';
Data['inerror'].asString := '1';
Data['inum'].asString := '';
Data['sensorid'].asString := '2322';
Data['ipversion'].asString := '0';
Data['tlsexplicit_smtp'].asString := '';
Data['host'].asString := 'server-dc1.domainname.co.uk';
Data['usewindowsauthentication'].asString := '';
Data['requiredotnetversion'].asString := '378389';
Data['simulate'].asString := '0';
Data['tlsexplicit_ftp'].asString := '';
Data['timeout'].asString := '60';
Data['exeparams'].asString := '"-u=domainname.co.uk\prtg.user" "-p=***" "-c=server-dc1.domainname.co.uk" "-n=server-dc2"';
Data['momopersistent'].asString := '';
Data['tlsexplicit_pop3'].asString := '';

Thanks in advance.

active-directory active-directory-replication-errors domain-controller