Yes. You are right. I was trying few things. I installed oes 2018 server as replication server under exising tree. But few things did not work well. I had problems during configuration. So I removed the OES 2018 from the ring and installed OES2015 SP1 OS on the server and configured it as replication server under the existing tree. Everythings worked well for a few days. Suddenly I saw change password problem in Primary server. But logging into the secondard server from Windows OES client would allow password change. Even this, after few days started give the password change error.
Don't do this please. It's expected that this works, but it's a *really* ugly workaround.
Did you try IR12 like I asked you? Did it help?
I found something that makes it work. If I change the setting in OES client -> Advanced Login->Nmas Authentication to Off, then I am able to change the password successfully. Let me know what is the meaning of this.