Premier Color changing profiles keeps lowering brightness.

When switching between profiles (e.g., sRGB, Adobe RGB) within Premier Color, the brightness just keeps going lower and lower, without modifying it.

E.g.:

• I start out at 70 on Adobe RGB
• Switch to sRGB and it becomes 43
• Switch to Adobe RGB and it becomes 57
• Switch to sRGB and it becomes 33
• Adobe RGB: 45
• sRGB: 27
• .....

How are these brightness values stored? After coming from sleep the brightness also seems to change, and I can't make head or tail on how this is 'managed' by which settings where.