This can happen very often on accident. People tend to remove friends and/or deny party invites accidently. They need something like when you remove a friend it says “are you sure?” (Next part is optional) and maybe another option between “Prevent further friend invites from “insert gamertag here-”?”. And for the parties well its the same thing “are you sure?” When denying and possibly a “prevent further party invites” because I had this problem many times.