Ahsai

The "W-line" is the only line to communication between the immobilize and the DME so any intermittent issue there will definitely explain your issue. Based on their description (fault code 23 and the tests they mentioned) it sounds reasonable to come to the conclusion of a bad ignition switch because that's also what the factory diagnostic manual recommends too.

DBJoe996

Hate to throw a kink in the present line of thought...but...when my original starter started to fail often I had to try many start attempts to get going. Hot or cold did not matter. Turn key to start...nothing. Repeat and repeat and nothing. Sometimes I felt like such an idiot at the gas station because even after four or five attempts to start...nothing. Then waiting and waiting. Then try one more time...starts. Replaced OE starter and that has never happened again.

speed rII

When my problems was on, I mean that the car would not start, I could not get durametric to connect Immobilizer ecu. Again, I suggest that you or your mechanic remove the ecu under the driver seat and clean it and it's wire connections.
Takes about 30mins and I will bet that the cause is there.