Most "the nest looks wrong" reports trace back to the input file: polylines that do not quite close, duplicated entities from a sloppy export, text and dimensions left on cutting layers. The DXF health checker analyzes a file for nesting readiness and reports exactly what it found.
Better: it fixes what it can. Open contours are closed within tolerance, duplicates are removed, and the cleaned file is returned to you. It is free, it works without an account, and it accepts files from any CAD that writes DXF.