Specifically, to give more info on what you wrote: Propane leeches oils out of non-propane rated hoses (or cheaper quality hoses). This oil moves into the buddy, pools and thickens, plugging up the metal piping.That's what I use for multiple days on the ice. Have to use the filter with the standard hose though, or it will destroy the fuel system in the heater. Going on 5 years on a refurbished portable Buddy I got for half price from Cabelas.
To lessen this, use expensive quality "bulk tank" propane rates hoses. Also, a regulator on the bottle will lessen hose pressure lowering leeching. Always use a filter with bulk lines as noted.
But, you can fully disassembly a buddy, remove the metal gas lines, soak them with carb or brake cleaner to loosen the oil then blow them out. Make sure you use soapy water to test pressure on all fittings when reassembling to catch leaks.
I've never had any issues with my buddy at any altitude staying lit. We use ours the most at a 7,700ft lake. I have a 5lb mini "bulk" tank, but I tend to just use small green "disposable" bottles. I refill those easily with an adapter i made (I dont use the cheap brass "refill" adapters so readily available, they dont fill the bottles enough). I dont have to worry about leeching or other issues plugging lines that way.