I've heard a bit more about that from Ft Knox: it seems that the problem may be with rounds binding in the feed chute or partially delinking from inertia or vibration during travel- thus a gun loaded on the nice, stable conditions of a firing range will work swell and perform as advertised for observers; one that's travelled on bumpy roads at varying speeds and cornered around a few city streets may not.
A couple of potential fixes seem possible, beyond a redesign of the ststems feed chute to something more akin the units used aboard aircraft guns of WWII and PT boat mounts: one being the use of the M9 link, which has a tab that snaps into the extractor groove of the .50 cartridge case, locking the round more positively in the link. This would require minimal modification of the M2 machinegun, but probably nothing insurmountable; alternately, the old tankers M85 gun that uses the M9 link could be fitted on Strykers, and since these guns offer a high/low rate of fire setting, [ca 1000 RPM on the high setting] could even offer a firepower improvement for the Strykers. And a pair of such guns on the Stryker's Remote Gun System mount, made to withstand the weight and recoil of the 40mm Mk19 grenade launcher, could be even more spectacular.
Until that can be worked out and turned into a field-usable kit, it's also possible that a pair of M240 7,62 NATO MGs might be substituted for the single .50 M2. It's not as if the Stryker crews are going up against other light armored vehicles, in which they'd fare poorly; what they need is the firepower to hose down RPG gunners and observers for mine detonations- 7.62 should do just fine, and if one gun of such a pair on the RGS should hand up, the other would probably still get the job done.
It's possible, though, that the Stryker armament setup is flawed beyond simple redemption and will require a complete reengineering and MWO replacement workover. If that's the case, you'll see the M2 .50s remain aboard the Strykers, and you'll see the enemy RPG gunners and sappers get bolder. And we'll lose more Strykers, and unfortunately, some more crewment in them as well. 
