Summary:
Trident, bow, spyglass, crossbow and shield not visible in Allay hands. If you give these items to Allay, they will be invisible in his hands, all other items are visible when allai is holding them.
Steps to reproduce:
Summon Allay.
Give Allay trident, bow, spyglass, crossbow and shield.
Observed results:
Trident, bow, spyglass, crossbow and shield not visible in Allay hands.
Expected results:
Trident, bow, spyglass, crossbow and shield visible in Allay hands.
To be more specific, any item with an associated attachable in the resource pack will appear invisible. I've tested with attachables of custom items and this is also the case.