UV Mapping Channel 2 effecting result (on play)

Unity Engine
1

Unity 5.6.1p2 / Enlighten / ShadowMask Baked Mode

Wondering if anyone could help me out - its probably something I am doing wrong but in my scenes I have road surfaces that are using a second UV Map to add an extra level of detail to the road. When I bake the results are as I expect, all my static objects leave shadows and the dynamic object use the real time shadows. This issue I have is when I hit play the roads 2nd channel gets completely ignored like its defaulted back to UV map channel 1. See comparison below - notice the dark tyre marks on play are all stuffed up only when I hit play thou.

3117021--235814--OnPlay_commented.jpg
3117021--235814--OnPlay_commented.jpg3000×871 531 KB

2

Found a fix - if I use UV Map channel 3 for the road its works. This confuses me now - because Generate UV’s is off so my 2nd Channel UVs are still there that same as before (which are the same as the new UV Channel 3) but now because the texture map is using UVMap 3 it works. Errrrrrrgh I am confusing myself.