I had that problem on some of the ist-d_ series. It was commonly reported of pentaxforums at the time.
I don't know how similar the e-dial position or type is to the K-x, but on ist -dS it is close to the corner of the sensor.
Also that e-dial switch is in a position under the wheel in front of a plastic cup shape, that it would be unlikely to have any spray reach through gaps in the rear cover, without running onto sensor.
Taking these cameras apart is fraught with problems like wires breaking, a nasty flash capacitor and getting things re-aligned on re-asssembly
Dead ist-ds, ( not k-x) rear main board photo
https://app.box.com/s/js3wi81n8dgu36odpcmne0l7082o2154
This photo just taken with my last working ist-ds! I still use it in my workshop with an old AF500FTZ flash and a Vivitar 28mm 1:20 Close Focus lens.