Chinese table tennis is full of such cases. This is their national sport, this is were they dominate.
Many Chinese players fall out with their brutal system. Either they barge and do nothing, like Liu Shiwen in the last decade, who was the very best player, but had some terrible losses to non-chinese players. Thus she was not allowed to play Olympics as World No #1. The most upsetting thing is that she lost to Ex-Chinese players, who left the system and played for Korea or Singapore. Some even for European countries, but only one ex-Top 10 player.
He Zhili played for Japan, Harimoto Tomukazu's parents also left the Chinese system at very young age and played for Japan. Last Olympics were extremely stressful for China because of this Ex-Chinese player who won against the very best, effectively unbeatable Chinese superstars, with new techniques. Then the Chinese looked very vulnerable because several European players also took that up and beat the GOAT Ma Long in a series of losses. Some 2nd rank Bejing politician took his chances and fired the coaches, the 3 best players defended their coaches and wanted to protect their superior system from some amateur destroying everything for his political chances. So the whole team was recalled from the ongoing World Championships, and didn't play for the next years. (Ma Long also had a knee injury). A new young Chinese protege didn't turn out to be winner against Harimoto, so after 3 years the old trainer at least in the men's team was allowed to come back, the old players won again, and China won almost all gold medals. They just lost one, even if they developed a secret win strategy against their biggest opponent, a young Japanese, and surprised them in the finals, but Liu Shiwen's partner fell off, and they lost Mixed Doubles. So Liu Shiwen is now forever dirty, not winning any Olympics gold. But she stayed in the system, and still is best paid player worldwide. She will probably retire this year.
However, no Ex-Chinese player ever won a gold medal against them. This would be their worst upset, it might even trigger a downfall of the political system.