Getting error message "Error: Add: Already Exists. <68>" when trying to modify a node in AD

Question

We have node as following

-CN=userMGMt,obapp=ABC,OU=myConfig,DC=dom1,DC=company,DC=com
 |-CN=seqNo=1,CN=userMGMt,obapp=ABC,OU=myConfig,DC=dom1,DC=company,DC=com
 |-CN=syncNo=1,CN=userMGMt,obapp=ABC,OU=myConfig,DC=dom1,DC=company,DC=com

Whenever there is update in application, the current seqNo is incremented (by renaming the current seqNo) and another node of syncNo is added (by incrementing previous value).

We are getting "Error: Add: Already Exists. <68>" while adding the "syncqNo" from aplication (we are also getting same message when we try it with LDP). If we search the new entry of syncNo through LDP we are not getting any result. But if we try to add the seqNo, we can successfully add it. The point to note that both "seqNo" & "syncNo" having same objectClass and same possSuperiors class.

What is the possible cause? Is there any other tool available on AD to view the data?

Any pointer will be quite helpful.