Steps to reproduce:

1. Download the attached project
2. Make sure that Spotlight - Red, Spotlight - Blue, and Spotlight - Green are enabled in the Hierarchy
3. Navigate to the Lighting Settings window and bake the lighting using CPU lightmapper and observe the resulting lightmap
4. Now bake the scene using GPU lightmapper
5. Notice that the bounce color is predominantly red

Notes:

- Only reproduces with overlapping spotlights
- Only reproduces when spot angle is set beyond a certain threshold (usually beyond 105)

Forum thread : https://forum.unity.com/threads/gpu-lightmapper-preview.561103/page-7#post-4302229

Also 2 videos showing the same issue:
https://www.youtube.com/watch?v=GeqbpZmCbZs
https://www.youtube.com/watch?v=0ZBaS-hWZE8