If you’ve made your way here, I feel you. I know how frustrating it is when you edit track information and shut down Traktor and it gets stuck on “Flushing background tasks”.
After searching high and low online and unable to find a solution, this is what worked for me. I checked for a Traktor upgrade in the NI Service Center and there was none. But there were a number of drivers that were available to install and I installed them all. I then restarted my laptop (as recommended) and went about editing track information, and guess what, there were no more “flushing background task” problems after that! This is a solution that works, I hope for you as it did for me. Ciao.
Note: This worked on Windows 10