Accidentals overlap the note head on augmented or diminished unisons in chords.

[kfxs]

const vf = new Vex.Flow.Factory({renderer: {elementId: 'output', width: 160, height: 160}});
vf.context.scale(0.75, 0.75);

const score = vf.EasyScore();
const system = vf.System();

const myChord = '(B4 B#4)/w';

system.addStave({
  voices: [score.voice(score.notes(myChord))]
}).addClef('treble');

vf.draw();

output:

The issue occurs both on bass and treble clef from line 3 to above:

const vf = new Vex.Flow.Factory({renderer: {elementId: 'output', width: 160, height: 160}});
vf.context.scale(0.75, 0.75);

const score = vf.EasyScore();
const system = vf.System();

const myChord = '(Bn3 Bb3)/w';

system.addStave({
  voices: [score.voice(score.notes(myChord, { clef: 'bass' }))]
}).addClef('bass');

vf.draw();

output: