A Precarious State
That the global economy is in a precarious state seems self-evident. Take your pick of the systemic risks: debt bubble and slowdown in China, banking/political crisis in Europe, negative interest rates and stagnation in Japan, ongoing meltdown in emerging markets and currencies, oil prices that threaten mayhem if they go up and if they go down, and a downturn in global trade that is usually associated with recession.
Other than that, everything's great. How about those summer Olympics? Seriously, what isn't in a precarious state?
If the global financial sector isn't precarious, then why is capital flooding into negative interest bonds? Why are money managers willing to accept a guaranteed loss of capital if things are going great and opportunities for low-risk profits are abundant?
The political realm is also in a precarious state. No matter how you interpret Brexit--as a Kabuki play by Deep State insiders, as a political ploy that went off the rails, as an ugly outburst of xenophobia, as a rebellion of the Forgotten Class that lost out in the Great Financialization boom, as a resurgence of nationalism--whatever interpretation or combination of factors you favor, the net result is the same: Brexit reflects a precarious state of shifting political tectonics that threatens the status quo.
It isn't just political certainties that are giving way beneath our feet--the global "recovery" narrative is crumbling like weathered sandstone on the edge of a cliff. No wonder institutional money managers, hedge funds and punters are all either fleeing to safe havens or entering trades with their thumbs twitching nervously on the "sell" button.
If the global banking sector isn't precarious, then why are bank stocks tanking? If these banks are minting profits and accumulating well-collateralized capital, why are investors selling them?
If everything's so solid, why is hot money chasing the bubble du jour? From copper to rebar to bitcoin to iron ore to silver, hot money is sloshing from one casino-sector to another on a daily or weekly basis--what's next? Bat guano? Disney dollectibles? Is this a sign of a healthy, sustainable market?
If you think so, I have a containload of hot bat guano to sell you--I guarantee it will be the next bubble du jour, you'll get rich overnight...
If the U.S. economy isn't precarious, why has the growth rate of new businesses collapsed to Depression-type lows? If everything is going great, why aren't entrepreneurs jumping in to mint all those easy profits?

The global political/economic state feels precarious for a good reason: it is precarious. Being told everything's rock-solid while the ground beneath us is rumbling isn't terribly persuasive, and some talking head reassuring us that the economy is still "growing" won't stop the tremors.
The fact we are near zirp and other countries are in negative rates itself shows the precarious nature of the market and everyone's economies at such low rates of growth also proves in itself the precarious nature of things. That said, zombie economies downward slide are incredibly stable however they are also sadly maligned from a free market economy and guaranteed to end badly. That's why they should be avoided.
That said, we have yet to see a strong enough event to make them pop. Two leading candidates are inflationary hoarding which is nil and monetary contraction caused by central bank actions which is almost inevitable because expansion can't go on forever without completely undermining capitalism and the fairness of the monetary system. That said, the Federal Reserve has a long way to go because politically and constitutionally they will have a hard time allowing negative rates on bank deposits (although they could issue Treasuries with it which would make you wonder who would buy them then) and Congress seems in no mood to support more QE given its already horrible track record of only enriching banks and bankers (exactly why the Federal Reserve seems to love QE).