Re-calculating model's lighting after resize?

So a resized model via Entity:EnableMatrix() is illuminated *flawlessly *as long as its X/Y/Z scale proportions are maintained the same (1:1:1). But when the model is resized with different X/Y/Z scale proportions, it’s no longer illuminated accurately when shined at with a lamp (or any sort of light):

The leftmost canister is the default size (1, 1, 1), the middle is thrice as big but with the same proportions (3, 3, 3), and the rightmost is with altered proportions (3, 0.5, 3). The left/middle are lit up correctly; the surface is exposed where it should be. The right one is flawed, parts of the model are still not lit while the lamp is aiming straight at them. I’m assuming this is because the ‘slope’ of the model doesn’t really change, and model illumination is slope dependent in relation to the light source’s position.

A few more examples:
[T]https://picload.org/image/rdgdggww/20160911014710_1.jpg[/T]
[T]https://picload.org/image/rdgdgrgr/20160911014329_1.jpg

So my question is, does anyone know of a way to fix this? Correct a model’s lighting using lua? It would be **awesome **if it can be done. Would greatly appreciate any advice or leads!

e: Also, I’m fairly sure it’s not bumpmap related, given that HL2 canister - as well as other props I’ve tested - don’t have a bumpmap.