Silas sounds like he can be challenged when action is NOT the right move. Where caution, talk or a steady reserve is called for. Something diplomatic or delicate where trash talk will lead to complications. If I interpret correctly, his INSTINCT is trash talk, which means it’s almost always his first impression to others. Challenging trait for a patrol leader.
Laurel is tricky but it sounds like you have some traction already. You could have something where her scent tells her something which disagrees with what the others clearly see as the right path. Do they trust her or go the way their EYES tell them? Nothing says she needs to be wrong of course!
Abram sounds like one who is interested in both looking out for his fellow mice and perhaps getting praised for it. (I don’t know the player/character so can’t really say) He is setting himself up to protect others and to always be prepared to do so. Challenge this with someone who distinctly DOES NOT want or need his help, or who resents being protected (openly at least)
Brand as wanderer said will likely cause trouble with a tendency to separate. He may also fail to be present when needed or distance may make him misinterpret a situation. The belief is interesting because on its face it sounds like he’s being bold, but it is a mouse’s nature to run and hide, so THAT is what cannot be tamed. Give him a situation where fleeing or hiding may jeopardize his patrol or the mission.