As can be seen in the image, sloped powered detector rails break when being pushed or pulled by a piston. This is the only type of rail that behaves like this which leads me to believe that this is a bug. It appears that the detector only brakes when it is powered while transitioning from a sloped shape to a flat shape.
Related issues
relates to
Attachments
Comments

[media][media][media][media]

Just checked in 1.14 and the problem still exists.