The lightmaps aren't working correctly on Unity 2017.2 and later when those were baked on Unity 2017.1 or before. In this case, the lightmaps were baked on Unity 5.6

To reproduce:

1. Download attached project "Miffy_Lightmap.zip" and open in Unity
2. Open "IntroScene" scene
3. Open the Game window and inspect GameObjects lightmaps

Expected Result: Lightmaps looks good
Actual Result: Lightmaps are broken - a lot of black spots, colors also are corrupted

Notes:
- This issue reproduces on both Windows and OSX
- This issue reproduces on Android and iOS
- This issue reproduces on Standalone builds
- In Unity 2017.3.0b1 issue starts looking much worse
- Issue image is in Comments section

Reproduced on Unity 2017.2.0a1, 2017.2.3f1, 2017.3.2f1, 2017.4.2f2, 2018.1.0f2, 2018.2.0b3 and 2018.3.0a1
Not reproduced on Unity 5.6.1f1, 5.6.5p4 and 2017.1.3p4
Regression on Unity 2017.2.0a1