Originally posted by another user
Unknown6 is a field within the RPC call, it contains a timestamp, a hash (unconfirmed) and some other unknown data that the official PoGo client sends with its RPC call,
up until recently sending Unknown6 as empty had no effect on the data you received from the server,
yesterday this changed and if you don't send a valid Unknown6 field then the server will return all of the map data as being empty.
So the devs who are reverse engineering are trying to find what data goes into Unknown6 so we can replicate it.
We currently have a good idea of the functions that might be generating the hash, but as of yet, we don't know what goes into Unknown6 ..