From a NewsTomato report dated May 14, 2018.
"According to legal sources on the 14th, A, an investor who used Upbit, brought an action last month for delivery of movable property, demanding that Upbit hand over the Bitcoin due under the payback event it ran last year.
Like other exchanges, Upbit collected fees generated when investors traded, and ran a 'fee payback' event returning 20% of the trading fees investors paid over the single month of December last year in Bitcoin, Ethereum and other assets. A too paid some KRW 347 million in cryptocurrency trading fees in December last year, during Upbit's 'fee payback' event period.
Under Upbit's own terms, 20% of those fees should have been paid at the start of this year once the event period ended — but far from receiving the fees, A could not even log in to Upbit. According to A, on being unable to log in and checking with customer service, A was told that Upbit had judged A's trading abnormal and blocked account access without prior notice."
"Attorney Jaesun Yoon of Law Firm Changchun, who represents A, argued: 'A was only able to log in more than two months after the account was suspended, by which time A had already suffered more than KRW 70 million in losses from the collapse in prices.' He added, 'Beyond that, Upbit is refusing A's request for payment of 20% of the trading fees without any particular reason. Despite taking substantial trading fees, it is not performing its undertaking to pay 20% of them.'"