I'm by no means an expert, but my understanding is that China's debt problem is not external debt, but internal debt. To put what the more negative takes are saying in US-related terms it's as if the mortgage-lending practices of the mid-2000s were done on a much larger scale (involving not just housing loans but almost everything funded by borrowing, including industry, infrastructure, etc) and for a much longer time.
As a result, there are lots of loans on the books that will never be paid off as things stand, and unlike the US there is no mechanism in the financial system to acknowledge any of that on a gradual basis (loan writedowns, etc), so the loans keep being rolled over instead.
At some point, reality will need to be faced, at which point there will be either massive financial system issues, much worse than what the US had going on in 2008, or huge government bailouts. And in the latter case, that implies even more financial repression or taxation, or both, than is already going on, with resulting decreases in economic well-being for urban areas in China, which is the thing that _really_ worries the CCP.
If the economy grows faster than the "bad loan" burden, then this problem is basically temporary, and rolling the loans over until the economy has grown enough to just deal with the issue is the right strategy. It's hard to come by plausibly correct (or even unbiased) estimates of either economic growth or the size of the "bad loan" burden, but almost all the estimates I've seen seem to agree that for a long time the "bad loan" burden was growing faster than the economy. Whether that's still the case, I don't know.