Yeah not sure what's up with that, I keep clicking unsubscribe but after a day or so they start again. But each time they start it seems to be from a different watched thread...
Go to the watches thread section. There’s a little drop down menu at the top. Click “disable email notifications”. That sorted it for me!
What @Joe Mac said. Go to https://www.needlesandgrooves.com/watched/threads and in the "Manage Watched Threads" box at the top-right, click "disable email notifications" and/or "Stop Watching Threads".