List of items that can't be crafted:

Roof_Cor_Hole
Roof_Hole
Roof_Triangle_Hole
Wall_Cor_Door_Vent
Wall_Cor_Gate
Wall_Cor_Vent

Also a list of items that make a wrong sound when punched or placed:

Triangular Steel Roof (wooden punch sound)
Triangular Steel Roof Hole (wooden punch sound)
Corrugated Roof Hole (wooden punch sound)
Steel Roof Hole (wooden punch sound)
Double Steel Roof Upper (no sound)
Double Steel Roof Lower (no sound)
Corrugated Gateway (wooden punch sound)
Steel Roof With Vent Slots (wooden punch sound/no placement sound)
Inverted Corrugated Ramp Wall RH (wooden placement sound)

Border pieces that can be damaged by low caliber weapons:
Border Wall
Border Wall Inside Corner
Border Wall Outside Corner

(vents untested)

Would also like to point out additional bugs. Building Materials x10 does not have an inventory icon. All border wall structures can't be crafted back into Building Materials x10 because the recipes for them are set to Border Wall Inside Corner.

If you fix the issue with border wall structures, please change the inventory size of those items to be bigger. If possible, Border Walls can be used to store 10 Building Materials more effectively than Building Materials x10 can.

Thank you very much, will fix this soonish.

the building material x10 don't have an inventory icon, it's space outline (the amount of inventory the item takes) shows up and the item dropped has a proper model