Synchronize_Configuration failing

I'm using F5 v10 and have Powershell script that uses iControl to make changes to active node and then sync it to standby node using synchronize_configuration. I'm using SyncMode::CONFIGSYNC_ALL. It was working fine till yesterday and suddenly started failing. The error message does not provide enough information. Any idea how to troubleshoot this error:

Error: System.Web.Services.Protocols.SoapHeaderException: Exception caught in System::urn:iControl:System/ConfigSync::synchronize_configuration() Exception: Common::OperationFailed primary_error_code : 16908289 (0x01020001) secondary_error_code : 0 error_string : Error synchronizing configuration: at System.Web.Services.Protocols.SoapHttpClientProtocol.ReadResponse(SoapClientMessage message, WebResponse response, Stream responseStream, Boolean asyncCall) at System.Web.Services.Protocols.SoapHttpClientProtocol.Invoke(String methodName, Object[] parameters) at iControl.SystemConfigSync.synchronize_configuration(SystemConfigSyncSyncMode sync_flag) at CallSite.Target(Closure , CallSite , Object , Int32 )