I think you are conflating present perfect progressive/continuous with present perfect.
In present perfect progressive/continuous, "has been" is followed by an -ing verb.
He has been running.
In your sentence however, "repaired" should be viewed as an adjective, so your sentence has the present perfect form of "to be."
Your device has been repaired.
Your dog has been ill.
But you are correct that using the past simple instead of the present perfect is usually an acceptable substitute.
Your device was repaired.
Your dog was ill.
The difference is subtle.
For the sentence about the dog, "has been ill," suggests that the dog is still currently ill, while "was ill," suggests that it may no longer be ill.
For the device however, the two sentences are virtually the same (probably because of the implication that if the device was repaired, then it still is repaired). Personally, "has been repaired" sounds a bit more formal than "was repaired."