I'm working on the gaskets and seal on my sm465 to np205 also. Here's a kit for them:
SM465/Figure 8 NP205 adapter reseal kit
www.offroaddesign.com
Looking at that kit, when you say you've replaced seal at adapter, do you mean the right side gasket or the seal?
If both that seal and right side gasket are working properly, I should think fluid would be contained in the np205 and not enter the adapter. Also, that seal prevents sm465 fluid from entering the np205. The sm465 fluid enters the adapter to lubricate the coupler inside it.
If you say you have fluid transfer, that means there are no leaks in the entire np205-adapter-sm465 assembly, correct? (There is a gasket kit for the sm465 as well, and one of those gaskets goes between adapter and sm465).