its a confirmed bug, Michael Brookes has confirmed they are working on it... hopefully it wont even need a patch just some serverside twiddling.
however ultimately at the end of it, it will just mean manure hauling is not the most lucrative career in the universe any more.
PS 576 credits.... pah! i have seen em for less than 100

(and yes it needs to be fixed, until it is i suggest you try something else in game unless they offer mats or commodities you want)