This is a known problem of the FBW Airbus. The problem are the USR waypoints that show up in your flightplan when planning a flight with Simbrief for example. You can delete them in the SID, but not in the STAR. When ever a USR waypoint shows up in a STAR, you have to either take over manually or head direct towards the waypoint following the USR waypoint in the STAR. Then it should work. Normally there would be a discontinuity that shows up in the MCDU flightlan, but they‘re replaced by USR waypoints the autopilot can‘t handle.