The previous owner of Mirage drew my attention to this 'biscuit' and said he had long suspected it was in the wrong place to prevent binding.
It this the correction position for the circular biscuit that the outhaul passed through?
(https://i.imgur.com/YXqK0NOl.png)
(https://i.imgur.com/szuZcVFl.png)
Right location, but wrong side up. The other side has very clearly "this side up" written on it :D
Also, there is normally a shackle there and the line has an eye-splice, whereas it looks like your line is tied straight to the outhaul car with no shackle and a knot.
Nice photo of Poole Quay. Is that where your boat is laid up?