How Hayek solved Sraffa's own-rate problem
It turns out it is the same way that Keynes solved it:
But Hayek had indeed, like Keynes, absorbed the lessons of the Sraffa exchange, and accordingly acknowledges that whereas the rate of increase of the physical amount of anyone input invested at an earlier date and the physical amount of the same input obtained at a later date may, and indeed will, differ for any two commodities, "the value equivalence in terms of the 'numéraire' at the two dates must bear the same ratio to one another for all commodities...The fact that Keynes, Hayek and Lachmann all see Sraffa's own-rate challenge as having been answered, and by the same answer that I see as meeting that challenge, gives me a fair amount of confidence I am on sound footing here!
This elucidation, we should note, is precisely the same as Keynes's own-rate setup in chapter 17." -- Tyler Beck Goodspeed, Rethinking the Keynesian Revolution, p. 120-1