... just a longshot but i know of annother person who made a game in the style like this. its been a bit but perhaps they might be of limited help. the person in question is named lipucd and they made a game called project qbee and a couple other thats been fogged over in my memory. perhaps they encountered this problem too and would know what causes it? granted its ancient rpgmaker stuff at this point so they may have forgot...
edit: some animation or such would be a good idea indeed. the question is what? from the dialog they are sorta like scammers... so flashing lights kinda effect maybe? could be pulled off by it simply cycling thru color to avoid giving a seisure...