Hey HowlingWolf698, If you have not already done so, please open a support case on our website or start a Live Chat for this issue. Please attach the screenshots you provided to me here as direct uploads, so that my colleagues can take a look. Thanks!
I have successfully completed 20 terrorist hunt / training ground missions and have not got the achievement for it. Attached are screenshots to prove it. https://photos.app.goo.gl/rEnDwK6fsDtfeGtV6