Locate the roof in the sliced preview
Move through the preview until you find the first extrusion that crosses the cavity opening. Record that layer’s Z and the previous layer’s Z. The insertion event must occur before that covering extrusion. A CAD roof dimension alone does not prove which sliced layer starts the cover because slicing planes and layer settings affect the result.
Account for the first layer
If the first layer is 0.3 mm and subsequent layers are 0.2 mm, layer 10 ends at 2.1 mm. It does not end at 2.0 mm. InsertPlan checks whether the supplied closing Z lies on the stated grid and rejects a mismatched value rather than silently rounding it. The displayed layer numbers start at one.
Validate the actual pause
Place the pause using the slicer’s supported command for your printer profile. Review the resulting preview again after reslicing. On a small test print, confirm that the toolhead moves clear, insertion is possible and the printer resumes with the expected next layer. Preserve that validated profile for the final print.