My 604 big bore motor used to produce a bit of condensed vapour and oil. I only know this because I had to have a catch tank on the breather to pass scrutineering.
Might be worth taking the filter housing off and giving it a clean out of any stuff accumulated over the years. Perhaps then intercept the breather hose and run the engine to see if anything is being blown out. When the rings went on my Morini you could clearly see vapour and droplets. Does sound like excess crankcase pressurisation due to worn bore or broken rings though.
"Do not adjust your mind, there is a fault in the reality"
1957 175 Sport