Reported here:
AppliedEnergistics/Applied-Energistics-2#8132

I don't know what immediatelyfast is doing exactly, but I'd assume it's due to AE2 replacing the model via Mixin when shift is held:
https://github.com/AppliedEnergistics/Applied-Energistics-2/blob/main/src/main/java/appeng/hooks/GuiGraphicsHooks.java#L46

Already fixed in latest dev build. You can download it here: https://github.com/RaphiMC/ImmediatelyFast/actions