The group's Vision Fund - which has made a string of global investments in large technology companies - suffered after Chinese ride-hailing app Didi Global announced it would delist from the New York Stock Exchange and pursue a listing in Hong Kong instead, due to pressure from Chinese regulators about data security.
In addition, the U.S. Federal Trade Commission moved to block a planned takeover of the Softbank-owned British chip designer Arm, by rival Nvidia in a deal expected to be worth $80bn.
And if that wasn't enough, just hours before, shares of Southeast Asia's biggest ride-hailing and delivery company Grab fell more than 20% on its Nasdaq debut.
The Vision Fund is Grab's largest shareholder owning about 18.6% of the company.
These latest disappointments have added to Sofbank's woes - over the last three weeks the group's shares have dropped 23%, as Softbank reported a second-quarter loss last month, after its Vision Fund plunged due to sharp declines in its portfolio companies.