Due to multiple operational failures by Nasdaq, UBS's pre-market orders were not confirmed for several houses after the stock had commenced trading," the bank said.
This resulted in the bank entering orders "multiple times" and left UBS with more shares than it needed – and those shares have since fallen almost 50% in value.
Facebook floated on 18 May when the shares were priced at $35 each and despite briefly rising above that level have sunk below that price leaving investors with losses. Last week Facebook's first results presentation as a public company failed to convince investors with revenues of just £750m for the three months ending 30 June and shares now trade around $10 below the flotation price.
On the day of the flotation, Nasdaq was forced to delay the start of trading in the new shares following a glitch in its trading system.
UBS, which has a new management team following the alleged unauthorised trading by Kweku Adoboli who faces a fraud trial in September, disappointed the market with its second quarter pre-tax profits of SFr951m. It has the first bank to reveal the international investigation into attempts to manipulate Libor but, unlike Barclays, has not been fined for any wrongdoings but said again that it was cooperating with the authorities.