Anyone ever had the crankcase vent tube clog?

 

I saw it happen on a Freightliner M2 propane delivery truck with a Mercedies engine. Luckly, the driver was loading his truck which was only idling. The crankcase vent tube froze up forcing the engine oil out the top of the engine. The driver noticed the oil running on the ground and shut off the engine in time. Freightliner put out a service bulliten to shorten the vent tube to prevent this from happening.