Start with what the failure looks like.

Lines do not bond, nozzle scrapes, gaps appear or corners lift.

Fine hairs, travel strings, corner blobs or wet-filament symptoms.

Clicking, thin lines, gaps, weak walls or inconsistent flow.

Layers move sideways, echoes appear, or walls show repeated bands.

Supports fuse, collapse, scar the model, or bridges sag.

Rough walls, seams, poor top layers, bad holes or incorrect fit.

The model moves, collapses or continues printing in mid-air.

Build-plate adhesion, supports, islands, exposure or release-force problems.