Login to iManager 323 using the treename (vas IP address) in the "TREE" field.
Now chose any task which leads to the object selection dialog, e.g Users > Modify User. There, chose the "simple selection" Tab, and enter a username you know exists.
Result: Fails. When you scroll down a bit, you will see an error "An internal error has occurred." The Details show: "Creating secure LDAP context failed: <treename>:636.
Now do the same, but login with the IP address of an eDir server in the Tree field of iManager. Now the same works.
There are some old TIDs dealing with that error that suggest to disable secure ldap, but that doesn't help, it only changes the error to Creating LDAP context failed: <treename>:389
The server running iManager *can* ping <treename> just fine, it's resolveable.
Same worked in iManager 2.7 on the same server (pre upgrade). Duplicated on plain SLES with eDir, as well as on OES2018SP2.
Sounds lile a bug to me?