Crossover one? Please be specific.
It seems to me that it's most likely the virus escaped when Chinese virologists lost containment. At that point, China went into deep cover up mode. They locked down all travel from "Wunan" within China. Yet somehow, at the same time, they were scooping up PPE and letting people they had to know were infected, travel to other parts of the world; Italy, Spain, UK, US, etc.