In my case, it is caused when Indigo RT sets a different aspect ratio for rendering in the active scene (for example, for a resolution of 1920x1080 or multiples of that) and when I apply these settings to the scene.
In the viewport, the different aspect ratio is typically represented by vertical or horizontal gray bars.
SketchUp 2017 (Make) does not cope with these settings of the render program during normal image export from the same scene and produces grey areas of different widths depending on the image resolution. Up to version SketchUp 2016 (Pro) this was no problem for me.
I use version 2016 Pro for work and 2017 Make for hobby (Animation, because MSPhysics only runs with 64-bit SketchUp).
Indigo RT (plugin "Skindigo") has in the menu "Skindigo Render Settings" a "Reset Camera" button, which also fixes this problem.
"Advanced Camera Tools" are, I think, a pro feature.
F