I had the same problem. first time I spoke to Tixx since he returned to Lions Arch was in LA overflow. He said he would give everyone who spoke to him a gift, and gave me the option to ask for one. I chose the option to ask for the gift but he gave me nothing. My bags were not full, and I had not spoken to him with any other character, in overflow or not. I have not received any gift from him on any of my characters. Now if I speak to him with any of my characters he says he cant give the gift twice, and to check the box beside him if my bags were full. The box looks open and I cannot interact with it.