Versions

Minecraft: 1.18.2
Forge: 40.0.34
Hex: Commit 767dd99
Paucal: Commit 8f64bef

Issue

Scrolls cannot be written to if there's already a pattern stored in the scroll.
For example, empty scrolls can be written to (Consideration, pattern, Scribe's Gambit) but after that, it cannot be written to anymore.
The error given in chat is:
operator expected at.petrak.hexcasting.common,items.ItemDataHolder in offhand but got 1 scroll
This bug was encountered on the supporter Hexcasting server.

(The janky mishap message is fixed on the bleeding-edge)

That's intended behavior.