To reproduce:
1. Run attached project
2. Select the "testScript" GameObject, on this you can see that each "Center Camera Target" gets gradually darker (target 0 is a cube map, this is then copied to 2 and 2 is copied to 3)
3. Open EditorCapture folder and notice that one capture is darker than the other (they should be identical)

Everything works as expected with build project.

Reproducible: 5.4.0a5 (6b220773f9c9), 5.3.0p1 (1e2decc4fa01), 5.2.3f1 (f3d16a1fa2dd), 5.1.4f1 (36d0f3617432),