Wandering Traders should go Invisible when a nearby Bell is rung.

When a bell is rung, villagers panic and rush to their houses. They also panic when they see a threat, and at night, they return home. Wandering traders drink invisibility when they are threatened. However, they do not drink invisibility potions when a bell is rung. I believe them doing this would help with the feeling of panic when a bell is rung.