Idiom: to be on a slippery slope – to be in a dangerous or bad situation which will probably only get worse.
Example: The economy is terrible at the moment. There are no jobs for the people and they have no money. The economy is on a slippery slope and unless the situation changes soon, we’re heading straight for a disaster.
Watch and see how the idiom to be on a slippery slope & idiom run-of-the mill are used in context by native English speakers!