Toshiba Corp. (TOSYY) shares fell in Tokyo Wednesday as investors questioned whether its choice of a Bain Capital-led consortium will ultimately lead to a quick sale of the troubled group's flash memory unit.

Toshiba chose a group led by Bain Capital Private Equity LP, but also supported by government-backed investment funds that has offered ¥2 trillion ($18 billion) for the world's second-largest producer of NAND flash memory chips. The group includes Korea-based SK Hynix Inc., the Innovation Network of Japan and the Development Bank of Japan and appears to have won the bidding contest despite failing to meet the ¥2.2 trillion price proposed by a paring of U.S. chipmaker Broadcom Inc. (AVGO) - Get Report  and Silver Lake Private Equity Partners.

"Toshiba has determined that the consortium has presented the best proposal, not only in terms of valuation, but also in respect to certainty of closing, retention of employees, and maintenance of sensitive technology within Japan," the company said in a statement. "Following this decision, Toshiba's intention is to reach a mutually satisfactory definitive agreement with the consortium by the date of its ordinary general meeting of shareholders, scheduled for June 28, and to close the transaction within March 2018."

Toshiba needs to secure a sale for its semiconductor unit in order to raise cash to satisfy the billions it must pay to its U.S. creditors as a result of the chapter 11 filing of Westinghouse, its U.S. nuclear unit, earlier this year.

However, the sale could be slowed -- or possibly cancelled altogether -- as a result of legal action from Western Digital Corp.  (WDC) - Get Report  , a former partner of Tosbhia's that has consistently said the auction process violates prior agreements between the two companies. Western Digital's SanDisk unit owns a 49% stake in Toshiba's main chip plant in Yokkaichi.

"Toshiba Corporation continues to ignore both SanDisk's consent rights and the dual-track legal process currently underway," WDC said in a statement late Tuesday in San Jose, Ca. "The language of the relevant agreements is clear: Toshiba Corporation has no right to transfer its JV interests to a third party without SanDisk's consent. SanDisk has not given its consent to any transaction, and will continue to protect its JV interests and preserve its rights through both its request for injunctive relief and the arbitration process."

Toshiba shares fell more than 2.5% to close at ¥322 each in Tokyo and have slumped more than 31% since the company revealed in late December that write-downs at its Westinghouse unit would be much larger than expected owing to cost overruns in projects in Georgia.