A bug in Twitter’s Android app caused video streaming metrics to increase by as much as 35%, overbilling advertisers that paid to run campaigns on Twitter’s platform.

Business Insider reports that an insider with knowledge of the error has confirmed that advertisers were overbilled by Twitter when a bug in the Twitter Android app falsely inflated video metrics by 35%. Twitter has reportedly refunded advertisers for the overpayment.

The bug allegedly affected social media video campaigns that ran between November 7th and December 12. How much the bug cost advertisers is currently unknown.

“We recently discovered a technical error due to a Twitter product update to Android clients that affected some video ad campaigns from November 7 to December 12,” a Twitter spokesperson told Business Insider. “Once we discovered the issue, we resolved it and communicated the impact to affected partners. Given this was a technical error, not a policy or definition issue, we are confident it has been resolved.”

Twitter has been under intense pressure recently to increase its ad revenue and attract new users as the company’s growth has stalled. Between the second and third quarters of 2016, Twitter’s monthly active users only grew by approximately 4 million. This error also comes shortly after a string of high profile departures from the company such as its longtime COO Adam Bain, VP of ad sales, head of media partnerships, and most recently its CTO and vice president of product. This month, a top equity research analyst claimed that Twitter as a company was “toast” and it’s stock was massively overvalued. The company also laid off 9% of its workforce worldwide in October.

Lucas Nolan is a reporter for Breitbart Tech covering issues of free speech and online censorship. Follow him on Twitter @LucasNolan_ or email him at lnolan@breitbart.com