Wall Street seems to be in a combative mood these days. Finra arbitration cases are up nearly 50 percent this year, and attorneys involved in the proceedings think they know why: the increase in market volatility.

"As Warren Buffett said, when the tide goes down you learn who's swimming naked," said Stuart Meissner, a securities law attorney and managing member at New York-based law firm Meissner Associates.

If that's the case, Finra's latest case filings numbers show there are a lot of players in the securities market suddenly running for towels.

Through April, 1,538 new arbitration cases have been filed with Finra, which is up 47 percent from the 1,047 cases filed at the same point last year. It also marks a 29 percent increase from 2016. The increases span cases filed by both clients and brokers, with client filings up 40 percent and intra-industry filings up 59 percent, according to Finra.

Attorneys involved in Finra proceedings said they weren't too surprised by the increase, noting that it's not unusual to see industry disputes rise as the market takes investors and their brokers on the type of wild roller-coaster rides that were experienced earlier this year.

But there may be other factors at play, according to Finra.

Cases related to Puerto Rico bond fraud and requests by brokers to have their Finra records expunged may also be contributing to the increase, according to officials at the agency.

Case filings involving municipal bonds, for example, totaled 279 at the end of April, up from 94 a year earlier, buttressing the claim that the Puerto Rico bond cases are a factor.

At the same time, Finra is proposing a rule change for broker record expungements that some in the industry feel would make it harder for brokers to cleanse their records when they've been cleared of violations. The theory would be that the impending change has compelled brokers to get their expungement cases in while the old rules remain.

A compliance consultant who formerly headed arbitration operations at Finra feels that all three factors—volatility, Puerto Rico bonds and the expungement issue—are playing a role in the surge of filings.

"Volatility for sure drives claims," said George Friedman, who served as Finra's director of arbitrations from 1998 to 2013 and now is principal of George H. Friedman Consulting LLC in Teaneck, N.J.

Friedman, however, noted there have been periods of volatility so far this year, but it has not been sustained. In years past, he said, it was virtually guaranteed that a sustained correction would lead to an increase in arbitration filings several months later.

He feels that although the Puerto Rico bond crisis has been ongoing for several years, filings may be up this year because attorneys are rushing to file their cases as they battle against the statute of limitations.

"On the customer side, I think it's predominantly the Puerto Rico cases," he said.

Securities attorneys heavily involved in Finra proceedings, however, pointed squarely at market volatility as the primary cause of the increased case filings.

"Investors get sad and worried about their portfolios," Meissner said. "They sell out and there are big losses."

Attorney Adam Gana, who defends investors in Finra proceedings, said he's seeing this trend in his practice, where there has been an uptick in cases involving theft and "selling away"—instances where brokers sell products not approved by their firms that turn out to be part of a fraud or Ponzi scheme.

The reason this happens, he said, is that it's easier to hide wrongdoing when the markets are thriving and investors are relatively content.

"As the markets go down, case filings go up," said Gana, managing partner at the law firm of Gana Weinstein LLP, with offices in New York and Chicago. "Bad markets expose bad portfolios."

It's not just investors who crank out the complaints when the markets go bad, attorneys noted.

Market volatility also often acts as a catalyst for brokers to switch firms, which leads to legal disputes, Meissner said. That’s become messier since many broker-dealers have made it harder for their brokers to leave after backing out of an industry protocol in which the brokers used to leave more easily.

"More firms are backing out of the protocol, meaning there are going to be more disputes," he said.