Its a re-occurring issue for other guns too. Hopefully Crytek have seen some posts. It has no player fix for C4 or JAWs unfortunately. The game has been known to correct the issue, especially after parts where the game takes control of your character or when you get your a*s beat up by a Tidal Wave / Ceth / Pinger, in a cutscene.
Your disc isn't defective.... well actually it could be. Always can make for a nice coaster for drinks later on though!