^$%4^AKX ⇒ China 78103D [FR24] [FlightStats] [FlightAware]
Country of registration: China
Altitude: on ground Squawk: 1275
Speed: 0 kt | 0 km/h RSSI: -17.1 dBFS
Track: n/a Last seen: now
Position: 47.921°, -122.274°
Distance from Site: 1.7 NM | 3.1km
Seems someone at Boeing being cute in flight numbers
-17.1 seems very quiet for that distance from your site. For that speed, I guess it’s on the ground. If it’s in a hangar, that could also help explain it.
It’s much more likely be a damaged message that happened to look like a BDS2,0 message. These messages are not particularly reliable to decode. I actually added something to dump1090 yesterday that requires them to be alphanumeric which should remove the worst errors.