How to reproduce:
1. Open attached project "ScaleFactorErrors.zip" and scene "SampleScene"
2. In Project window, select "Ball" object
3. In Inspector window, change "Ball Import Settings" -> "Model" -> "Scale Factor" from 807691 to 807692 (one higher) (works with any higher number than 807691)
4. "Apply" the changes of the object
5. Observe Console window

Expected result: no errors are thrown
Actual result: every time Inspector window is updated in any way an error is thrown (clicking anywhere, dragging on preview window, changing to other tabs: Rig, Animation, Materials)

Reproducible with: 2017.2.0b1, 2017.2.3p1, 2017.4.4f1, 2018.1.2f1, 2018.2.0b5
Not reproducible with: 2017.1.4f1, 2017.2.0a4

Note: the highest number you can use in "Scale Factor" depends on the starting mesh size