Chinese electric vehicle maker Nio (NYSE:NIO) stock exploded higher last week, rising 25% on a surprisingly strong monthly delivery update. The EV maker said it had delivered 15,620 vehicles during April, a massive 134% increase over the year-ago figure. That brought its cumulative deliveries since starting to almost half a million EVs.However, investors should still use caution. This unexpected good fortune of the leading Chinese EV company just might be as good as it gets.A Surprising U-Turn for Nio Stock ...