In his interview, Murry seems to indicate that the technical irregularities the NSA experienced last year started its predicament. According to The New York Times, those technical problems contaminated the agency's database with information it had no authority to collect. Officials were forced to purge hundreds of millions of call and text logs it got from phone companies as a result.
If you'll recall, Snowden leaked the NSA's surveillance activities to the media back in 2013. This particular program gathered domestic phone calls' metadata that shows callers, recipients and the time of contact. It allowed the agency to find associates linked to terrorism suspects. Under the program's original form, phone companies had to hand over all the logs they collect to the government. The USA Freedom Act approved in 2015 due to intense backlash from Snowden's revelations softened its power to an extent. Now instead of automatically handing over data to the agency, phone companies keep what they collect and only give investigators access to records relevant to a terrorism investigation.
While the Freedom Act cut down the number of records the NSA collected from billions per day to a few hundred million per year, its scale remained huge. The agency got access to 151 million call logs in 2016, even though it only obtained court orders for 42 targets. In 2017, it got its hands on 534 million records despite investigating 40 suspects only.