For reference: There is a duell in the module where a shaman tries to secretly help one NPC by continously casting Cure Wounds on him while supposedly only helping him “stand up” after he intentionally let‘s himself fall prone. To spot this, a PC has to specifically declare checking for interventions a then suceed a DC 15 perception-check despite being within earshot…
Glad someone else knows it. As a player who frequently had to transcribe spells into roll20, I always just assume other people know the components certain spells take to cast and then end up confused if they don’t.