I noticed that some spartan shields are still held in the wrong orientation. Rectangular shields that are similar in shape to vanilla are fine.

But "round" shields are the ones that have issues
Shield with guard down:

Shield with guard up:

Alex's mobs shield of the deep also suffers from this

And lastly Immersive engineering's heavy plated shield

Which is a shame since IE's shield is one of the best looking ones out there.

I can't correct each item's visual position from other mods. I guess the author of the mod used a different way from vanilla to render the shield. It can't be fixed unless the mod creator decides to modify it.