EDIT: The issue seems to be completely fixed in v1.14.20 (Win10 and Switch)
I bought the Biome Settlers Skin Pack 2 by Minecraft in the marketplace and saw that most skins inside this skin pack have issues. They do not display the items in their hand correctly in 3rd person.
See screenshots (taken in Windows 10, v1.14.1), I added the default Steve for comparison. The screenshots were taken in singleplayer. However, other people on Multiplayer also can not see the items in my characters hands. The items are visible for me in first person.
Platform: Windows 10 and Nintendo Switch.
Reproduce: Yes, every time I use some of the Biome Settlers Skin Pack 2 skins (like the Mooshroom Archer) the items turn invisible.