Part of mesh is invisible in game window but it's normal in the editor window

I have 4 layers:

  • Layer 1: (buttom) is a large sheet of
    hexagons mesh;
  • Layer 2: green sheet
    mesh;
  • Layer 3: red path mesh;
  • Layer 4: (upper) the number labels in
    canvas.

Things are okay in preview in editors, but not in game mode.
Anyone has any idea why this is happening?
This issue is totally random!!! It only happens sometimes, even I didn’t change anything.

If it’s z-fighting, bring purple mesh a little closer to camera, and reduce distance between clipping planes of your camera (bring near plane further and far plane closer)