By default AutoCAD 2016 is configured to switch current tabs or even model space should your cursor momentarily hesitate over one of the tab previews. This situation has happened to me more than once and is especially annoying when my current drawing is quite large and takes minutes to switch tabs (or space).
Fortunately there is a variable setting that gives you full control of this interface rather than leave you at the mercy of an accidental switch.
By default the variable FileTabThumbHover is set to 1. Per AutoCAD Help: A setting of 1 will "load the model or layout in the drawing window when you hover over a file tab thumbnail." As your cursor passes over the previews, all it takes is one moment of hesitation to activate an unwanted tab switch via by hovering over it.
Set your FileTabThumbHover variable to 0. From now on, you need to click the thumbnail to activate it rather than hover over it. No more frustrating accidents and, in my opinion, a much more intuitive way to interact with your thumbnails.
Also explore the other file tab variable setting to suit your needs:
The default setting of FileTabPreview is 1, which displays thumbnail images. A setting of 0 displays a list of tabs rather than thumbnails.
The AutoCAD command FileTabClose turns off the file tabs. FileTab turns them back on.
The read-only variable setting FileTabState tells you if your tabs are on (1) or off (0).
Notes from Cadalyst tip reviewer R.K. McSwain: This is a good tip, especially if you not using a powerful workstation. The delay in switching drawing previews could be annoying on anything but the fastest CAD machines. Test the first two mentioned system variables for yourself and see what your preferences are.