Almost all computer controlled cars use a 5 Volt reference to things like cam, crank and throttle position sensors.
I have not measured a "known good" E46 camshaft sensor connector, however, I have reason to believe you should have 5 Volts, or very close to it at a disconnected camshaft position sensor connector.
Low Voltage means too much Voltage drop or a partially grounded wiring harness (bad or corroded connection or possibly a bad solder joint in the DME where the connector pin meets the main board). Worst case you may have a more severe problem requiring the DME to be replaced, which I would suspect would be a worse case situation.
Flashing the DMW will not cure a low sensor supply or reference Voltage. Also adaptations are always moving and resetting themselves. If you manually reset them, you just force them back to baseline to start from a default, usually speeding the process up a bit if you make changes to the engine.
I would check the reference Voltage to the other camshaft position sensor if you can easily disconnect the connector. Then I would check the reference Voltage directly at the DME with the sensor and the harness disconnected, then connect just the harness with the sensor still disconnected and see what values you measure.
Check the the pins in the harness at the DME are clean and tight when you have the harness disconnected.
You should be able to figure out quickly if the problem is the DME, harness or connectors.