Golf IV / Jetta IV :: CEL On Exactly 6 Seconds After One Out Of 5 Starts At Minimum

02 Jetta GLS Turbo 1.8. The car runs perfectly fine, and has good power, but one out of 5 starts at minimum it sets the check engine light exactly 6 seconds after starting the engine. It is most commonly a P0340 - Cam Position Sensor Circ Error, I'd say 70% of the time. The other 30% of the time it is a P0011 - Camshaft Position Timing-Over-Advanced. And once or twice it set a P0012 - Camshaft Position Timing-Over-Retarded. It will only ever set one of the codes. I clear it after it sets, and it will never set the code while driving the car.

- I've double-checked the timing belt, and it is spot on. Could not ask for a more perfect lineup of the timing marks.
- There is no noise or rattle on cold start
- The car carries good oil pressure and I'm on a fresh change with Pentosin 5w40
- I checked continuity on the outer two pins on the cam position sensor with a result of 1.910 ohms.

What I should be looking for next? Almost spent for a new cam position sensor, but hate to throw money if there is something I could test to narrow this down. I can't find any test procedures in the Bentley manuals, but maybe I'm not looking in the right spots. The index has no mention of the camshaft position sensor.