I'm a little surprised Wiswind or someone else with personal experience with these things hasn't responded by now. Just off the cuff, I'd try to lower the catch can. With it lower, the oil in the line will be more likely to drain into the catch can instead of being stuck in the line. The oil may be only going in the line part way and draining back into the valve cover. In your pix, it looks like maybe you could reinstall it to the back side of the engine right off the back end of the valve cover and intake man and swap the two lengths of hose putting the filter closer to the PCV. If lowering and relocating it doesn't work or do enough, then I would install some sort of oil shield baffle inside your filter can to make the oil hit it on the way in and then fall to the bottom. I assume you hooked it up with the same airflow direction as indicated on it for an air line . Without the baffle, the airflow may not be slowing down enough to cut loose the oil. I would make the baffle out of sheet metal or a piece of pipe that can be jammed in tight in the center like a full height filter element with openings at the bottom to let the air in. When the lacking oil issue arose, did you confirm you had airflow (or vacuum)? And you are certain you have no leaks. Maybe try using a carb cleaner or like around the line to see if you have a leak.
Wiswind has said the catch can doesn't accumulate much when it gets warmer, but I have no idea what it's like with cool temps. That's my
