Asobo aircraft and Custom airport ILS problem

Using the FS2020 SDK, I have built a new airport at Sawmill Bay, NWT in Canada. This is the site of an abandoned airport built in 1943 to air-lift uranium ore from a local mine to the US for the Manhatten Project. The two runways are clearly visible in Google Earth, as are the roads, and the  remains of the nearby airbase buildings. The facility was used for a few years after the war as a fishing and hunting camp, but this operation was abandoned by 1969 due to radioactive contamination in some of the buildings and the soil. 

So my problem is that Asobo/Microsoft supplied airplanes don't work with the ILS I put in, but the third-party planes I have (that have ILS capable autopilots) do. Specifically, the Asobo planes show the proper behavior on the VOR gauges or PFD - the DME distance, and the Localizer and Glideslope bearing pointers work as you would expect, but pressing the NAV button on the Autopilot just causes the word VOR to flash for a few seconds on the PFD, then go back to ROL or HDG. Pressing APPR has no effect; the autopilot won't capture the glideslope. When I re-spawn the game with a third-party aircraft like the OZX G21 Goose Redux II, the autopilot behaves as you would expect: it captures the Localizer and Glideslope and flies down to the runway threshold perfectly. BTW, the default scenery for this location does not contain any airport data, so there's nothing existing in the Asobo scenery that my airport would be in conflict with.

Has anyone else stumbled on this problem or knows how to fix it? I never had Navigraph installed, and I've already tried the Package Reorder Tool to force this airport to load last, but nothing I've tried will fix this. The C-172, Cub Crafter NX, C-208, Beech Bonanza and Baron - all resolutely refuse to work with my Custom Airport ILS's, that work just fine with 3rd-party airplanes. FS2020 is now more than 5 years past initial release date, and it's kind of annoying that bugs like this still haven't been fixed. Or is this not a "bug", but simply a policy that Asobo-supplied planes won't work with Navaids defined in Custom scenery files in the Community folder?