Thank you for the clarification on your platform. I checked out your battlelog profile http://battlelog.battlefield.com/bf3/soldier/Silent%20Killz%20V1/assignments/855582044/xbox/ and on there everything seems to be in order. Did you recently update BF3 and then after wards the kills did not track? If that is the case the expansion which is contained in the file Multiplayer Update 3 (Close Quarters) - 2.4 GB may have been corrupted during the update. With this being a possibility I recommend to go to your download history and re-download the CQ expansion and see if that corrects your problem.
One additional clarification is that kills, assists, etc are not retro active on assignments. For example you may have hundreds of TUGS assists but an assignment does not look at your combat records to say that you've already met that requirement. You have to complete that particular part of the assignment after the assignment is unlocked so you will need to get the TUGS out again when that assignment is unlocks and get the required number of assists. That may be another thing that is happening.
@silentkillzv1 wrote:
Thanks for the reply, in answer to your questions; I play BF3 on xbox 360, I haven't deleted any files from my HDD recently, I haven't deleted the CQ expansion (if that's what you mean), and lastly, I only play on ranked servers.
Thanks for any help you may be able to provide.