Shares of Rocket Lab USA, Inc. (RKLB) plummeted 7.1% in post-market trading on Monday, wiping out recent gains as investors reacted to a disappointing third-quarter gross margin forecast and a likely delay in the debut of its Neutron rocket.

The sell-off was triggered by the company's second-quarter earnings report, which revealed mixed results alongside a cautious outlook. While Rocket Lab posted record quarterly revenue of $234.1 million, beating estimates, it reported a loss of $0.08 per share, wider than the $0.06 to $0.07 loss analysts had expected. The key concern for investors was the company's guidance for third-quarter GAAP gross margins of 29% to 31%, which fell significantly short of the 37.6% consensus estimate. Management attributed the margin compression to a shift in its product mix, with lower-margin satellite platforms expected to account for a larger share of future revenue.

Adding to the pressure, Rocket Lab appeared to push back the timeline for the first flight of its Neutron rocket. The company now aims to deliver the vehicle to the launch pad in the fourth quarter rather than launching it then, with CEO Peter Beck noting that the window for a launch before year-end is narrowing. The Neutron program is central to Rocket Lab's effort to compete for larger commercial and government missions, and the latest delay contributed to the post-market decline, despite the company reporting a record backlog of $2.36 billion and entering over $1 billion in new contracts so far in the third quarter.