I think I can add some information to this, seeing as I seem to have the same problem.
The Eden Editor works fine before you start a mission preview, but when you leave the preview to come back into the editor your camera controls will be frozen.
If you go into the map view and try to doubleclick to move the camera there it wont affect the 3d view and the the icon will kind of stick to "the points the camera were attached to before it broke" (The attached pictures show how the camera kind of sticks)
It should also be noted that a (for lack of a better name) "seeker lines" appear and follow your mouse, like when you bring up your map while in the actual game.
Without mods I don't get this problem all that often but I get the problem every time I use these mods; (ACE3, ACRE2, BlastCore A3, JSRS and the ShackTac Fireteam Hud)
This issue started happening yesterday, both with and without mods but the fact that the mods seem to be able to bring out the issue each time is interesting.