I have actually experienced this with my Mavic 3 classic, Specta Air, and my new Air 3. Waypoints have suspended when the point was set at 15 ft and during run it descended to 6. Three different drones , same thing.
This will be an excellent question for Monday nights pilot institute Q&A on you tube.
Maybe they're aligning with the DJI paranoia that is working it's way through.
You said said you had no trouble in other locations before.