I've been monitoring CHP for years with Uniden and GRE-manufactured scanners, and I've never had an issue with these "dropouts" you speak of. I always put the CTCSS tones in for the area I'm interested in monitoring, and that eliminates the annoying interference I often get from nearby electronic devices. Without CTCSS, the scanner will hang on continuous static sometimes.
Also, back in the days when the Valley Gold was on 42.120, CTCSS was necessary to lock out Oakland CHP, which transmitted on the same frequency with a different tone.