Yeah, interesting. It looks like it might be module-specific. There's a weird thing going on with the NPC sheets where @{pb} is actually tied to CR level. This doesn't affect anything in the repeating_npcaction section, because the +hit field is hard-coded. This in itself is potentially an issue - these stats are supposed to be de-linked for NPC's, and their bonuses all hard-coded. If the HP, AC, and general stats don't increase when you bump their CR, nothing else should be changing. Possibly worth bringing up in the 5e sheet thread. As you've dug up from the Attributes & Abilities page, these NPCs are doing the default sheet behaviour of adding the relevant spellcasting stat (@{charisma_mod} in this case) and the proficiency bonus (@{pb}) derived from the monster's CR level.... but then adding @{spell_attack_bonus} on top. The sheet doesn't usually do this, for obvious reasons: @{spell_attack_bonus} is just [[ @{charisma_mod} + @{pb} ]], you add one or the other, not both. Out of interest - what happens if you delete an offending spell, then drag a new copy in from the Compendium? I haven't been able to reproduce the behaviour you're seeing, so I'm assuming it's Frostmaiden-specific on these NPCs. Good detective work, by the way!