Editor's note - This story originally referred to Stonehaven as a "new" map added with the Onslaught DLC pack, when in actual fact it's always been available in the game. We apologise for any confusion caused.

Player complaints that a recent update for the Xbox One version of Call of Duty: Ghosts introduced performance issues, particularly on one of the new Onslaught DLC maps, appear be accurate, according to tests run by Digital Foundry.

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Following the release of the patch early last week, which coincided with the launch of the Onslaught DLC pack , players began noticing issues with Ghosts' framerate on Xbox One. This prompted Digital Foundry to examine the issue, including the new Stonehaven level that has been most frequently cited by players as experiencing problems."Kicking off with a look at Stonehaven, it's immediately obvious that things are not quite right," states Digital Foundry's report. "While the game does indeed hit 60 FPS in this stage, frame-rates are dramatically impacted when the whole level is in view, with metrics varying between 46-60 FPS as we run across the landscape. As frame-rates fall below the desired 60 FPS target, we also see the appearance of some screen-tear, adding some judder, making drops in smoothness more noticeable."In addition to this, looking down the scope of a sniper rifle can drop the framerate to the mid-30 frames per second range, a far cry from the 60 FPS norm the Call of Duty series is known for.Other maps were also put to the test. "[T]he drops in performance are far less severe, with momentary dips occurring during more hectic moments of play or when explosions and alpha effects are rendered on screen," Digital Foundry writes. "Controller response is much more solid, and we don't get the feeling that gameplay has been compromised to anywhere near the same extent as we saw on Stonehaven - the experience remains mostly smooth, even though there's a distinct feeling that things aren't quite as stable as they were before the latest patch was installed."Activision has yet to offer any explanation for these issues or a timeline for when a patch resolving them can be expected.What makes this situation odd is the fact that, at launch, the Xbox One version of Ghosts was regarded as smoother than the PlayStation 4 version -- albeit at the expense of being upscaled to 1080p from 720p, whereas the PS4 version runs natively at 1080p.

Chris Pereira is a freelance writer who spends his spare time agonizing over the final seasons of The X-Files. Check out what he's saying on Twitter and follow him on IGN