For decades now the concept of a catchcan on crank case breather tubes has been the solution for oil being cast up these tubes and into air boxes and/or just out and all over things. Its really just an expanded area where particles and oil mist slow down because of the size, collect or condense on the sides, run down and back into the engine case. As we have been having this issue with our diffs and gear cases I suggested using any type of inline fuel filter that can be placed vertically, should be just as effective. A member found this one on Amazon and installed it. So far it has ended his problem.
https://www.amazon.com/dp/B0753F6PF4?ref=ppx_yo2ov_dt_b_product_details&th=1Sense I too have been having this problem even after reducing the level to what the book calls for, I also bought one and installed it. Here's a pic of how I did mine on the rear.
It comes with a replaceable fuel filter which I decided to leave in to stop any passage of particles either way. It fits the vent tube a little tight but a quick twisting of a flat-blade screwdriver in the tube helps greatly. This can be done on any machine, front and/or rear. Simple and cheap.