Update - I took it for a ride this evening and everything behaved well, except for needing to use the tool to bypass the locked out shifting lever. Crazy.

I read in a post HERE post658948 that there is a manual adjustment to the interlock. Is this my next step? I've read a lot of people have this problem and it is cured with a repaired RCM (seems common, but I just had that done) also read a lot of people who had this problem ended up replacing the entire shift assembly (which seems crazy - it's an 05, with under 34k on the clock.)

I get it, they're finicky. I'm calling this domestic exotic. Merc repair bills dressed up in a Chrysler suit. ?? Frustrated here.