Two voices sharing a stave and a register must not lattice their beams through each other's noteheads

When two voices run continuous short-value beamed passages through the same tessitura on one stave, the upper voice's beam (above its stems) and the lower voice's beam (below its stems) can weave through the middle of the staff and strike the OTHER voice's noteheads even with zero real voice-crossing. The fix is structural (separate staves / open score), not a nudge.

A fugue exposition authored with voice2/voice3/voice4 (SATB grand-staff layout) instead of openScore, where two voices in the same register both carry sixteenth-note runs.

matches Gould's recommendation (Behind Bars, ch. 'Fugue and contrapuntal engraving') to give independent contrapuntal lines separate staves.

This rule needs the notated content and the rendered result together — the score says what should happen, the page says whether it did.