If it switches to 2 when
C-band connected there, then it doesn't sound like a switch problem, since the switch is switching there. I'd start to suspect the cable between the switch and the Ku lnb. Check to see if it's shorted or open.
EDIT: Also, can I assume that you are powering LNBs via analog receiver, and are using DC-blocks or one leg pass splitters to isolate power from dvb receiver?