Newly released legal papers alleges that Facebook knew about the data errors that presents inaccurate number of views on video since 2015.
However, Facebook described the case as lacking merit as they denied suggestions they had tried to hide the issue.
In September 2016, Facebook admitted that it had overestimated how much video people had watched for the previous two years.
"We told our customers about the error when we discovered it - and updated our help centre to explain the issue," FB said in a statement.
The error affected a Facebook metric called "average duration of video viewed", which was supposed to tell publishers for how long, on average, people had watched a video.
However, the metric did not include viewers who had watched for less than three seconds in the count.
Discounting the shorter views - including people who had ignored a video in their news feed, inflated the average viewing times for each video.
FB was also criticised for counting a video as being viewed after three seconds.
The plaintiffs allege that Facebook knew it was misreporting metrics by January 2015 but never fixed the error, and dramatically understated the impact. Their review of around 80,000 pages of Facebook documents obtained during court proceedings showed a “company mentality of reckless indifference toward the accuracy of its metrics.”
‘’While Facebook told advertisers that the error never affected billing, the plaintiffs wrote that grossly exaggerated video metrics encouraged them to spend more on the platform’’.