CaliKid,
Thank you for your email. The National Archives (TNA) were being a little disingenuous in their response to you, because while - technically speaking - the files aren't "missing", they should have realized which ones you were referring to, in view of the extensive media coverage and public interest. In any case, I'm not aware of any recent update, and so far as I'm aware the position is this: the MoD had undertaken to redact the 18 files and send them to TNA "by March". This should now have happened. But TNA have previously said they are likely to need another 9 months to prepare the files for public release, so sometime around the end of this year remains the best current estimate. That said, if TNA forego the sort of proactive media release they've done previously for MoD UFO files, and simply put the documents online, they shouldn't need 9 months. So, realistically speaking, the files might be released anytime between now and the end of the year.
I hope this is helpful.
Best wishes,
Nick Pope