“When I place a house mesh on top of the ground mesh in the PlayCanvas engine, I experience a flickering issue while moving in First Person. It looks as if the ground mesh is jittering up and down while the house stays static, or sometimes the ground remains static while the house jitters. However, as soon as I stop walking, both the ground and the house become static and stable after about 0.5 seconds.”
It’s likely both the ground mesh and the house mesh have polygons on the exactly the same spot … and so sometimes one renders, other time the other. Try moving the house just a tiny bit higher. Or remove those overlapping triangles from it (that needs to be done outside of PlayCanvas)