Astral Sorcery Version:1.12-1-6
Cavern Mod Version: 1.9.1
Minecraft Forge Version: 14.21.1.2387
Minecraft Version: 1.12

While Astral Sorcery is installed, any Diamond Swords, Hexcite Swords, Diamond Axes and Hexcite Axes cannot be placed in the Cavern Mod's Compositing Magic Book interface. Even after Astral Sorcery is uninstalled, any spawned/crafted Diamond & Hexcite Swords/Axes cannot be placed in the Cavern Mod's Compositing Magic Book interface, but ones newly spawned/crafted after Astral Sorcery is uninstalled will work without issue.

How to reproduce:
Have Cavern Mod 1.9.1 and Astral Sorcery 1.12-1-6 both installed.
Spawn in a Diamond Sword, Hexcite Sword and a Compositing Magic Book.
Hold down right click while holding the Compositing Magic Book to activate it, the attempt to place the Diamond Sword, Hexcite Sword into the storage interface.

*I have also made a bug report on the Cavern mod's GitHub about this exact same issue.

This was fixed by the mod author of Cavern mod as of Cavern Mod 1.9.2. This issue is now invalid, and closed. If anyone is having this issue, update to the latest version of Cavern Mod