I have had this same issue for a long time. Start to fire a weapon and it just wont stop firing. Even if you change weapons, it just keeps firing that also. This game is totally broken, i have never played a game that is this buggy and broken, every time i feel like i have fixed an issue, you throw another issue at me. It happened in Division 1 also. With a controller and a keyboard and mouse. I updated my computer recently and i still have many of the same issues i had with my old computer.
Yup, unfortunately, this auto-firing issue has been occurring since The Division 2 released back in March 2019. I use an Xbox controller and periodically this problem occurs. To another user's point, it seems to come and go which I wonder if this is a server-side issue or client-side and perhaps related to lag. I've experienced this will multiple Xbox controllers and ruled out a hardware issue since it has happened with each.