Even that steep drop may not be the end of it. Over the past month, executives of the company have bought tens of millions of dollars of its shares and approved an additional $150 million stock buyback by the company, moves that helped support Tianhe's price. All the banks that led Tianhe's public offering — Morgan Stanley, UBS and Bank of America Merrill Lynch — declined to discuss Tianhe with the AP. For Morgan Stanley and its Asian private equity chief investment officer, however, the fallout from potential trouble at Tianhe could be especially difficult.