In this example, the user wants to create/convert a Solid Edge part to Sheetmetal part using "Part to Sheetmetal" with the direction pointing "inside" - if, for example, the user wants to create a box within a box - the feature will fail with the warning/error:
This is because the "Gap" (in this case input as "1,00mm") seems to be measured from the outside of the box, so if the gap is set to 1mm, and Material Thickness is set e.g. to 3mm, the resulting Sheetmetal would intersect by 2mm.
Therefore the user has to keep Material Thickness in mind and to add this value to the wanted gap.
In this case, a value above a gap of 3,1mm would solve the issue: