The waters have been choppy for NBC News in recent years, with its “Today” franchise having ceded ground to ABC’s “Good Morning America” and its Sunday-morning mainstay “Meet the Press” struggling to find a new identity after the death of longtime host Tim Russert. Amidst that chaos, Brian Williams was supposed to be the anchor – in both senses of the word.

Now Williams, whose “NBC Nightly News” is the most watched evening newscast in the United States, has added to the challenges facing the NBCUniversal news division.

There have been no signals that NBC News is taking Williams off the air or readying any sort of disciplinary action in the wake of a disclosure Wednesday that he has on multiple occasions falsely stated that he was on a helicopter shot down by enemy fire while on an NBC News reporting trip in Iraq in 2003. Yet the admission seems to stack another pile on the plate of NBC News President Deborah Turness.

Since joining NBC News in the summer of 2013, Turness has not had to focus overmuch on Williams and his program. Despite inroads made among key viewers by ABC’s “World News Tonight,” particularly under its new anchor David Muir, Williams and “NBC Nightly News” have been more or less unassailable. Indeed, “Nightly” has beaten “World News” among viewers between the ages of 25 and 54 — the audience most coveted by advertisers — in both December and January, according to data from Nielsen.

Instead, Turness has appeared to place more emphasis on “Today,” a battleship of a TV program that puts more hours on NBC each week than there are in Fox’s entire primetime lineup, and “Meet The Press,” a Sunday-morning institution that hinges on getting key newsmakers to divulge something eyebrow-raising.

Under her aegis, “Today” has added Carson Daly to its ranks, burnished its image as a place for harder news (though it’s still prone to chasing sillier stuff) and pursued an executive to oversee the entire franchise — not without some difficulty. “Today” topped “Good Morning America in both overall viewers and viewers between the ages of 25 and 54 on Wednesday, January 21 – the first time it has done so in five months. Even so, “GMA” won more viewers in both categories for the week ended January 26, according to Nielsen — as it has continued to do for many months.

NBC News changed the host of “Meet The Press” in 2014, ousting David Gregory in favor of Chuck Todd. The show on January 18 notched a second-place win, and its best numbers in about ten months.

Now Williams will require attention, as NBC News tries to determine whether his falsehoods will damage his credibility as a news anchor. Williams has told the story for years, during an appearance on David Letterman’s “Late Show”  and at various public functions, of being aboard a whirlybird shot down by enemy fire in the Iraq desert. He only conceded he was not telling the truth yesterday in an interview in Stars & Stripes when U.S. Army servicemen who had been aboard the aircraft in question challenged Williams’ account, noting that he was never aboard the Chinook helicopter at the heart of the story and instead was on a helicopter that followed the damaged one.

“I would not have chosen to make this mistake,” Williams said in the interview with the military newspaper.  “I don’t know what screwed up in my mind that caused me to conflate one aircraft with another.” He also posted an apology on his Facebook page and offered similar sentiments during Wednesday night’s broadcast of “Nightly News.” The Iraqi incident took place before Williams took over the “Nightly News” anchor desk from Tom Brokaw in 2004.

What makes Williams’ admission worse, according to one person familiar with the situation, is that he had been counseled in the past by senior NBC News executives to stop telling the story in public. The advice, this person said, was not heeded.  One person familiar with current NBC News operations disputed that information.

Williams’ version of the story has never been allowed in NBC News programs, according to three people familiar with the unit. Indeed, in a March 2003 episode of “Dateline,” Williams described the helicopter trip accurately. “On the ground, we learned the Chinook ahead of us was almost blown out of the sky,” he said while narrating a report.

The way in which the story has transformed under his telling may prove unacceptable to a news audience, suggested Doug Spero, an associate professor of communication at Meredith College in Raleigh, N.C., who has worked at various New York TV-news outlets. “A memory loss is OK, if it is a minor detail about something in a story, but when you are personally involved in an incident there is no room for compromise.  I have always said, ‘I believe you until I can’t believe you any more.’ This may be that case.  All we have is our credibility.  Once you lose that, your general worth has been lowered.”

Williams’ disclosure comes not long after NBC News has had to retract or further bolster reporting claims during important stories that were later found to be inaccurate or challenged. Earlier this month, NBC News chief global correspondent Bill Neely reported that suspects in France’s Charlie Hebdo killings were dead or in custody — information that was incorrect. Williams reiterated the details about six minutes later, echoing Neely’s findings. The TV journalists had to retract the claims, and acknowledge the government-intelligence sources they had relied upon did not give sound facts.

Roughly a week ago, NBC News reported that Sgt. Bowe Bergdahl, the U.S. Army sergeant who was held captive in Afghanistan for five years after leaving his post before being rescued, was to be charged with desertion. The Pentagon denied the reports, and NBC News updated its report with new statements, though it did not admit its reporting was inaccurate. To be sure, many news outlets make mistakes, and correct stories as circumstances warrant. These examples came to pass on prominent events.

Can NBC News truly do anything? There are precedents, of a sort. MSNBC, which is also owned by NBCUniversal but supervised by an executive other than Turness, has suspended prominent personalities in the past.

In 2010, Keith Olbermann was suspended for two days after it was discovered he had made political donations to three Democratic candidates for Congress, a violation of NBC News ethics policies. Joe Scarborough was suspended that same year for the same length of time after Politico discovered he had made donations to political candidates. At the time, MSNBC and NBC News were more closely linked.

Williams is more or less the face of NBC’s signature news division. To reprimand him is to cast aspersion on the entire operation. In December, NBC News took time out to celebrate Williams’ ten years as anchor of “Nightly,” releasing a series of archive clips highlighting major moments from his decade behind the desk. A promo narrated by actor Michael Douglas touting Williams has made the rounds of NBC’s air and its various digital properties And NBC News recently signed the anchor to a new contract, reported by the Los Angeles Times to be valued at $10 million a year over five years.

Has this recent episode tainted the network’s newscast, or will it fade as the next trending topic surfaces in the rapid-fire social-media news cycle? NBC – and its rivals – will have to monitor the ratings to find out.