Forcing A Server Save/Database Update After A Trade?

[DY357LX]

How would we go about forcing a save/database write (update?) after a trade (with NPC) is completed?

I've had reports of players buying vehicles, logging out then logging back it and still having the cash that was supposed to be consumed by the trade.

Maybe a forced save wouldn't be CPU efficient if used on all traders, maybe just use it on weapons & vehicles traders.

Any ideas, anyone?
Thanks.