I installed the latest version currently available 2.4.23 The same bug still exists in this version.
So I can for sure say this is not related to ITS#6070
Since this is a major loss of functionality I would kindly ask someone to h= ave a deeper look at this.
I confirm it is related to ITS#6070; only, that ITS could be fixed (read: worked around) differently.
I don't think this qualifies as a "major loss of functionality" for the vast majority of the users of OpenLDAP. Solving this issue the right way (and few others) would require to advance OpenLDAP at least to 2.5 or 3.0, because a significant portion of the ABI would need to change, so do not expect to see it solved any soon.
In the meanwhile, you can try to use an instance of back-ldap as the translucent local storage, and place slapo-rwm on the database of the remote server that acts as local. I haven't tested it, so there might be minor issues, but I don't expect anything like this one.