That is a strange one, remember it does not have to be an Easy Find LNB now your set up, any universal LNB will work. The LNB is ALWAYS the first thing to be blamed, but now and again it is the LNB. It does no harm to have a spare LNB sitting around anyway.
They do fail, but usually they go dead (Like one I came across today) usually I find when there are dropped transponders its a bad/loose cable. Again like today, water had got into a ground block (Not my install, I use waterproof grease in all outside connections) and the connection had been arcing for some time, caused the LNB to go bad.
Not suggesting anything like that with your set up : ) Just an example of a typical LNB failure.