CanvasRenderer OnEnable SetAlpha

I am using the CanvasRenderer.SetAlpha() function to fade out UI elements. It works well most of the time, but at one position I deactivate gemeobjects, and when they are activated again, the CanvasRenderer's alpha value is reset to 1 instead of keeping the value it had before. Is that the intended behaviour?

Edit: A short test tells me it already happens in OnDisable() (or earlier, Debug.Log in OnDisable returns 1, while in Update it prints the correct value)

 

Issue still present in 2017.3.0p1

 

The problem still exists in 2018.4.10f1