I am having similar issues with my Kona3 and 7.5.1 NDD drivers with FCP 7.0.2.
When trying to scrub in the timeline, I’m not seeing any updates on my external monitor and it tends to become sluggish as well and randomly freeze.
The solution I found was to enable the VANC tick box. This eliminates the problem of not updating in FCP, but introduces a new problem since I work in HD and SD, my SD materials will have the VITC information transferred from SD captures. I hope Kona fixes the problem quickly. This is driving me up the wall!