High sulfur + dirt could be caused by adding some cheap, crappy high sulfur, dirty crude oil into the bunker fuel. A real kicker is the chlorinated hydrocarbon contamination.
Chlorinated hydrocarbons are not a significant component of crude oil nor are chemically produced in oil refining. They are present in a number petrochemical processes in one way or another.
First, cut some cheap, crappy crude oil into the bunker fuel to lower the cost per gallon of some middle man while selling to the ship consumer at market price. Second, the chlorinated hydrocarbons likely come from adding hazardous wastes that normally are disposed of via specialized and expensive incinerators or cement kilns. Some thousands of $$$ per barrel legal disposal costs.
There likely are “finger prints” in the contaminated bunker fuel that can be traced up the supply chain to track to the companies and persons involved in the apparent corruption. Analytical lab data is admissible in court as long as properly certified lab quality control information is paired with it. Singapore is a bad place for bad people to run afoul of the law.
Normal practice is to take constant fuel samples during a transfer and if contamination is detected you stop the transfer. Then you reject the sale.
You don’t just keep filling because it will spoil all your fuel.