It occurs because the image scale returned by a successful plate solve is different from the value configured on the plate solve tab.
This is an easy fix, other than changing the text to "Bad X Scale" which isnt useful to a single human on theThere are two possible reasons for this message:
1) The plate solve was a false solution (usually the cause) and produced a bad image scale value.
2) The user incorrectly set the image scale on the plate solve tab.
So, "ERROR: Check Image Scale" would be misleading in most cases as the user may be tempted to adjust the image scale instead of realizing the plate solve was at fault. And, the length of the text is too long for the grid. It would get clipped in its column in the grid, or force all of the columns to the right, limiting the data visible unless the window is expanded.