SoftBank Group Corp’s Japanese mobile subsidiary begins trading in one of the world’s biggest share offerings.

SoftBank Corp shares plunged more than 14 percent in their debut on Wednesday, as investor appetite for Japan’s biggest ever IPO was hurt by a recent major service outage and worries over its exposure to Chinese telecom giant Huawei.

Following its $23.5bn initial public offering, shares of the telecoms unit of SoftBank Group Corp fell as far as 1,315 yuan ($11.71) by early afternoon, or 12.3 percent lower than its IPO price of 1,500 yuan ($13.34).

SoftBank Corp shares were the most heavily traded on the Tokyo Stock Exchange’s first section, and closed at 1,282 yen ($11) or 14.5 percent lower than its IPO price.

SoftBank Group lost 0.9 percent and the broader Tokyo market eased 0.4 percent.

Softbank is listing more than 1.6 billion shares, roughly about one third held by its parent company. The blockbuster IPO is seen as part of SoftBank boss Masayoshi Son’s strategy of transforming from a Japan-based telecoms company to a global hi-tech investment firm.

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It will help raise cash for Son, whose SoftBank Vision Fund is worth an estimated $100bn and has taken stakes in some of the hottest tech firms, including Uber, Slack, WeWork and Nvidia.

The IPO was just shy of the world record $25bn 2014 listing of Chinese e-commerce giant Alibaba Group Holding Ltd, a SoftBank Group portfolio company.

During the IPO period, Japan’s third-largest mobile phone network provider by subscriber numbers suffered a rare nationwide service outage, which it said would not affect earnings or dividends.

Customers were unable to text messages or make payments via mobile phones during the outage, which was resolved after several hours.

Adding to investor worries, SoftBank Corp’s relationship with Huawei Technologies Co Ltd came under scrutiny as governments around the world moved to shut out the Chinese firm amid worries its gear could facilitate Chinese spying.

“There was a disruption in its network early this month as well as Huawei’s issues,” said Tetsuro Ii, chief executive officer at Commons Asset Management.

“There hasn’t been good news involving SoftBank recently.”

Sejiro Takeshita, professor at the school of management and information at the University of Shizuoka, blamed the disappointing start on questions over SoftBank’s growth strategy.

“One big worry among investors is the musical chair game that Soft Bank has been playing on, growth after growth, expansion after expansion – they are all worried when the music will stop,” he told Al Jazeera.

“It hasn’t. But if you look at the external environment of the telecommunications side, in Japan … growth is definitely winding down,” he said. “And you’ve got pressure from the competition and you’ve got the government trying to lower prices – so you’ve got a lot of pressure surrounding this industry as a whole.”