The main symptom of the coming crash in China is its foolish accumulation of toxic USD undertaken for no other reason than to keep the yuan low to export even more goods to America to buy even more USD.
In doing so, the Chinese are making the classic mistake of confusing paper wealth with real wealth. The amazing thing is that this folly has been exposed by Adam Smith as early as in 1776. It almost looks like 18th century again in China.
What is mercantilism in the first place? In a nutshell, mercantilists are paper bugs. They are ready to work day and night in the sweat of their brow, consume very little, but tirelessly produce, produce, and produce finished goods for the foreign market. In exchange, the foreign partners would happily offer them their own finished goods, but mercantilists would have nothing to to with them. Instead, they would accept nothing but paper. They would lock that paper in the box and sit on that box and imagine that they are rich. The specifics can vary. In the 18th century, bullion was the trading currency, so mercantilists would accept bullion in exchange for the goods. Today gold is a relic of the past, so the modern mercantilists accept pieces of paper that represent a commitment by the US government to print other pieces of paper. The ancient mercantilists were less stupid than the modern ones. At least the supply of gold could not be increased at a whim of some foreign government.
Which is another way of saying that China's leaders don't have a clue about economics and are still very much in the pre-Adam Smith mindset.
China's determination to support exports at any cost is foolish because it makes life better everywhere else in the world except China itself. The Chinese consumer still does not have cars, computers, refrigerators, or even lead-painted toys because everything he produces gets shipped abroad and because with his own artificially cheap yuans he cannot buy any of that stuff that Americans and Europeans buy essentially for free with their artificially expensive dollars and euros. As a compensation, the Chinese consumer gets news releases showing that his government has imported a record number of USD per capita. But since people can't eat dollars, especially when they are stored in a government vault and especially when the decision has been made not to import anything that dollars could possibly buy, this means the Chinese consumer gets essentially nothing. A Marxist would say that Chinese Communist Party is turning China into a colony whose labor resources are exploited to the full by foreign capital, and the Marxist would be right.
Already in the 18th century, people have realized that this policy is not only foolish, but also unsustainable. Wikepedia has this to say about accumulation of paper wealth:
"Hume famously noted the impossibility of the mercantilists' goal of a constant positive balance of trade. As bullion flowed into one country, the supply would increase and the value of bullion in that state would steadily decline relative to other goods. Conversely, in the state exporting bullion, its value would slowly rise. Eventually it would no longer be cost-effective to export goods from the high-price country to the low-price country, and the balance of trade would reverse itself. Mercantilists fundamentally misunderstood this, long arguing that an increase in the money supply simply meant that everyone gets richer. "
But there is an important point that even Hume missed. If a country that exports goods and imports bullion then throws all the imported bullion into the ocean, then it's back to square one, and the process can be repeated forever. And China does just that. It keeps a reserve to the tune of $2.4 Trillion. Every year dollar inflation eats away some 7-8% of this reserve, and every year they export some more goods to refill the coffers again. That's definitely an improvement to the original theory. If the classic mercantilists were idiots, then the modern mercantilists in Beijing are idiots to the second power.