Vulcan cam position sensor woes.

98 Ranger. Not the version of the sensor that eats shafts up. Intermittently I get the P0304 fault code. Every single time I can just clear it and it'll be gone for another few weeks, but then, randomly, it occurs again. Hot, cold, at start, while running, any RPM, rain or shine. I replaced the sensor (and not the shaft) just for the hell of it, but no change. I tested the new sensor's Ohms, and plugged it in and rechecked the pins at the ECM plug, and got the same readings each time, so the wiring seems OK. Yup, shook the harness around too. The shaft it rides on isn't loose and there does not seem to be any gear lash from the "flag." First, are there any known issues that can cause this behavior? RI? I replaced my spark wires before this all started. Bosch, dunno about the shielding.