I don't know if this helping in this case, but I just discovered that a companion can screw up some things. Cyrus was with me and I tried to talk with Jack at the big tower at the coast. Jack attacked us immediately. Same thing with a robbed merchant on the road to Ardea.
If I am alone Jack and the merchant talk normal to me. So, I ask Cyrus to wait just out of sight and this trick works fine.