Broken wafers
I used to be a bench tech a few years back and saw this happen on KX170B's primarily, but the 175 is very similar. The tuning on these radios is done by a system of wafer boards that rotate as the knob is turned. They sometimes break and inop frequency ranges occur.
I'm not sure if fixing this radio would be cost effective, and if I'm not mistaken, a KX-175 is illegal to use anymore because of the lack of frequency stability of the transmitter. (I think the FCC outlawed the KX-175 a long time ago). I think King made a KX-175B that might still be legal. You could ask an avionics shop if you could use a KX-170B in the same tray. Sorry I can't help anymore since I don't have access to the paper manuals anymore and they did not digitize them.
