This happens also with other visitors. Geyda, Azzuro and Solmar the Slaver just have two different "interactions", after the first dilemma is resolved, they should come only to sell items, buy slave or test subjects, but they are also treated as "presitigious" visitor with zero prestige and security, probably the script that stop them to be recurrent visitors failed. The others just come as recurrent visitors (the old ones), also in circumstances in which they should not. It's fine Lord Simroc come back from time to time since you helped him, not so fine if he return after you killed him