My second TIVO 2 uses a Comcast DTA50 set top box. It passes all the test for setting up and changing channels. Tivo test with CH 2 - 22 or so. When I programmed to record CH 198 (MHz) it recorded Ch 19 instead. QUESTION: is there a problem with 3 digit channels? Why would the system be unreliable in this case when it changed properly on all tests?