This affects all items with non-cube 3D models, like Immersive Engineering's Cloches, any item patched by Vanilla Tweaks' 'Item Stitching Fix' resource pack, Botania's Petal Apothecary and Mana Blaster, and almost everything from Create. See screenshots:

View from inside the drawer in Spectator mode:

Forge 40.1.84
Titanium 3.5.6
Functional Storage 1.18.2-1.0.7

Update: this issue seems to have cropped up after updating forge to 43.1.56. Issue #130 mentions it's working in 43.1.55.

Steps to repro -

1. Create custom profile for Minecraft version 1.19.2 and Forge version 43.1.56 in CurseForge app
2. Add Functional Storage to pack
3. Create a basic world with cheats on, no other special settings
4. Enter creative mode upon spawning
5. Select one spruce 1x1 drawer, and 64 clay balls from cheats inventory
6. Place drawer into world, facing any direction
7. Place clay balls into drawer
8. Enter spectator mode and look inside drawer, facing outwards to the front face of the drawer

Forge 43.1.56
Functional Storage 1.19.2-1.0.7

It's actually a separate issue from #130 specific to 3D items, flat items not being visible is due to a forge regression