It appears that global illumination can be overridden by bad values from the cache (either 0s or corrupt). In this case the cache values were created by using a Range shader parameter to control a Vector3 emission value.

Repro Steps:

Repro

1) Open attached project (“GICACHEBUG.zip” at the bottom, NOT the project attached with the initial report)
2) Open scene “UNITY_PASS_META_BAKE_BUG”
3) Clean GI Cache
4) Select object “Capsule” and set material parameter “METPASS Emission” to 0.5
5) Set “Global Illumination” dropdown to “Baked” and wait for bake to finish
6) Set “Global Illumination” dropdown to “None”
7) Open shader “MetaPass” and change line 30 to “fixed _METAPASS_EmissionMultiply;"
8) Save and go back to unity (wait for compile)
9) Set “Global Illumination” dropdown to “Baked” and bbserve how lighting is baked and then disappears
10) Set material parameter “METPASS Emission” to any other value and observe correct lighting