It is not really a bug, rather a opinionated choice to scale the pixels to the min distance between each pair of pixel. This can be however circumvented by using an explicit size with sizemode="absolute" or we introduce a min size relative to the scene.
To reproduce

import magpylib as magpy

magnet = magpy.magnet.Cuboid(polarization=(1, 1, 0), dimension=(.1,.1,.1))
sens2 = magpy.Sensor(
    pixel=[(0,0,1), (0,0,1.1), (0,0,1)],
)
magpy.show([magnet, sens2], backend='plotly')

Originally posted by @OrtnerMichael in #793 (comment)