I’ve had a few issues working with Tp_viper or curve2polyline (and polyline2polygon) free form parametric curves. Namely there seems to be nm-scale offsets when instancing them on another cell instance’s pin, as shown in the picture.
When using gds hierarchy under (no multiple of 90 degree) angles or in between grid-point translations, the snapping errors (better: delta’s) you see are fundamentally caused by looking at two non-aligned discrete coordinate systems on top of each other.
Interconnects within a single cell are by default not instantiated and snap to the same parent grid. In contrast, the Vipers are now child cells in your example, each in their own grid system. If you flatten topcell “nazca” in your example you will enforce a single parent grid to snap to for all structures in cell “nazca”.