pixi3d: Textures smaller than 200x200 pixels do not render with Sprite3D

Using pixiJS v7.2.4 with pixi3d v2.3.1

// Does not work
let a = new PIXI3D.Sprite3D(commonAssets.rabbit1); // 25x25 PNG
let b = new PIXI3D.Sprite3D(commonAssets.rabbit2); // 199x199 PNG

// Works!
let c = new PIXI3D.Sprite3D(commonAssets.rabbit3); // 200x200 PNG
let d = new PIXI3D.Sprite3D(commonAssets.rabbit4); // 400x400 PNG

Many thanks for any ideas. Amazing library!