Vehicles that fight on the losing side, or are destroyed in a win, are out of commission. They score nothing — and one on a winning team blocks stage progress.
Officers can reset any time: it repairs every vehicle, and grants Repair Parts — more the higher the stage you reset from (400 at stage 1, 22,735 at stage 95). Unused parts vanish at the next reset.
Clans' real behaviour, estimated from the public stage chart: when they reset, from which stage, how many parts that earned, and when they seem to have spent parts on repairs.