How to reproduce:
1. Open the attached '1212002.zip' project
2. Open 'SampleScene' Scene
3. Select 'ExampleGradient' GameObject
4. Select HDR Gradient Editor of Example Gradient dropdown in the Inspector
5. Notice that Mode is set to Fixed
6. Change Location value from 51% to 50%

Expected result: Quad is red or green
Actual result: Quad is yellow

Reproducible with: 2019.2.20f1(6.9.0, 6.9.2), 2019.3.0f6(7.1.7, 7.1.8), 2020.1.0a22(7.1.7, 7.1.8)
Could not test with: 2017.4.36f1 HDRP is not introduced, 2018.4.17f1 unable to set gradient color because quads are complitely white

Notes:
- Video and project of reproduction attached in Edit
- Reproducible on macOS
- Reproducible with Random Number node when Seed is Per Particle, Per Particle Strip; Not reproducible when Seed is Per Component