Well, it's not so simple as just replacing the NAND flash chip. It has to then be programmed with the (secret) Garmin proprietary OS before it can work. Outside Garmin (who won't take devices for direct repair), it'll be very difficult to find someone near you who has both the required reprogramming kit and special skills to do that.

Garmin does offer a replacement "one-for-one, like-for-like" on many recent devices however i don't know if they exchange KW GPS modules. They used to charge around US$200 + shipping i think for exchanging portable devices, so it might not be worth the expense even if they'll do a module swap or sell you a new programmed one.

Anyway, just hope it's not got a physically damaged flash and keep trying software solutions before looking at hardware repairs as a last resort. Unfortunately, because i don't have access to a similar DNX xx60BT i cannot experiment using any suggestions before passing to you. Regardless i'm pretty much out of ideas anyway now without getting hold of a similar device. You seem to have mastered the procedure for flashing via Updater in preboot and resetting as laid out in the old thread so if neither QC3 or Cure3 works now to get it into MSM i don't have any more to offer.

If you get a bit more hands-on experience, you might end up as our resident KW guru. Now that there's no posts in the forum lately by the much-valued expert members ORAK, kunix, Lolypop000, Alexander2010 et al. we seem to need someone to fill the gap. I'm sure if one of them or someone else with specific KW experience saw this and answered in this thread, they'd be of far more help than me.