Moto-Netix refuse to pay Deposit back after Can-Am caught fire

I traded my vehicle, VolkswagenTiquan in on the Yellow Can-Am and a cash deposit of R20 000.00 was paid via EFT. I collected the Can-Am even though it was not yet registered on my name and I informed Moto-Netix the same day I collected the Can-am that there were technical problems. They informed me to return the Can-Am. On my way to them, the bike caught fire. I was willing for them to repair the bike and find another seller. Unfortunately after 10 months they failed to find another buyer. Werner, owner at Moto-Netix agreed to return my vehicle but refuse to refund my Deposit of R20 000.00. The odometer of the Can-am when I collected it on 30 November 2016 was 23902.60 and when I collected the Tiquan on 9 September 2017 it was 24220.00. This means between Moto-Netix (while repairing and testing) and myself, 317 km was travelled. The odometer reading for the Tiquan on delivery to them was 196 915km and when I collected on 9 September 2017 was 202154. This means 5239km was travelled by Moto-netix since the vehicle was traded in on 30 November 2016. There is no reason for Werner (the owner) to keep my deposit. In actual fact he used my vehicle for 5239km. What about this costs? I would like for Werner to explain himself why he refuse the refund my deposit.