When you are on a solo group mission and you type "/group leave" when bots kill you and enter this command just before you get "Returning to home station" message, you leave the group but you have the group mission still active in the Missions tab and you can do it as if you were in a group. After it happened to me for the first time, I was able to reproduce it on third attepmt - you just have to enter the command in the right moment.

I can confirm this. Happens to me too.