I've only recently been in the "game" so not sure if my opinion will count, however the few I've sold so far, they are valeted and mechanically inspected on arrival/before they go on sale.
Deposit, I don't take them, the way I see it, if they change their mind, less hassle for both, if they want it, they'll be back anyway. I am a little flexible, i.e if some says they' ll be back tomorrow, i'll give them till midday next day.
With regards to the pedal, if you were confident there was no fault, you should have made it clear that is the way it is, or there is nothing to fix.
We keeping learning though :-)