In a lawsuit, WeWork accused SoftBank of putting "its own interests" first when it abandoned a plan to buy up to $3bn of shares from other investors.
Softbank also said it had failed to restructure its business in China, one of the conditions of the rescue deal.
A WeWork special committee, created last year to negotiate the rescue, on Tuesday accused Softbank of deliberately blocking the restructuring.
WeWork last year accepted a rescue deal from SoftBank, at the time the firm's biggest backer, which provided more than $5bn in financing and a pledge to purchase up to $3bn in shares from other investors.
However, the deal was criticised as too generous to ousted WeWork chief executive Adam Neumann, while SoftBank has also faced increased scrutiny over the chequered record of investments such as WeWork.