There are several methods available to find and compare any differences between layers.
After loading all layers into FAB 3000 (i.e import Gerber, ODB++, 2581, etc.), use the command Compare Layers. Menu: Tools / Compare Jobs and Layers / Compare Jobs and Layers / Compare Jobs...
Important: Make sure to set the error tolerance size to 1 mil (0.0254 mm) or less. The default value set is 2.5 mil (0.063mm) which does not produce the best values.
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