James, please see this FAQ:
Mosaic basically just reflects the return from the UPnP server to the command sent to it . Depending upon the server in question and its configuration this may not be what you anticipate as many server applications do not necessarily fully adhere to DNLA spec. MinimServer does which is why dCS have decided to limit their support to it.
So your problem is with Minidnla as all that Mosaic is doing is displaying the information that Minidnla is sending it.
I am sorry that MinimServer has a limit of 65000 folders but if, as in my case, folder = album, then I would doubt that software would be likely to be developed in the anticipation that an amateur user would have a collection exceeding 65000 albums. That might be encountered with a national collection such as of the Library of Congress or The British Library 
. I am afraid that you may be virtually unique in this respect. You could raise this issue with MinimServer on their forum of course: