Even though I select the entire screen to record, after a second or two the screen shifts and chops off the left hand side. I've used Camtasia for a long time on desktops and portables and never had this problem. Camtasia Studio 8.5 worked fine on my SP 3.
I'm having a similar problem on a Surface Pro 4 and Camtasia 8.6. About a half-second in, the recording cuts off the top third of the screen. I've tried changed screen resolutions, etc., but still no joy. Just a black bar along the top ... help us TechSmith!