The "Sludge" is called heavy ends, The vaporiser acts like a mini refinery and breaks/refines it out. It is mostly the strnch that is added to the gas at the terminal.
Generally if you will cool the vaporiser you will not get as much. You only need 120-140 degrees for the vaporiser to do its job. Yes most anyone can rebuild the vaporiser or mixer if you get a kit and FOLLOW THE INSTRUCTIONS that come with it. Your Local Propane supplier Should be able to order you the nessisary repair kits to do your repairs.
Regards