Pretty bizarre results. There are sometimes 2, sometimes 3 distorted copies of the IR. Does the sweep sound normal? A smoothly increasing-frequency tone? There doesn't appear to be any output device/output selection in the REW preferences for those so the system default will be used, but shouldn't particularly matter. There may be dropouts in either the sweep (which would be audible) or the capture (which wouldn't, but that can be checked for by looking at the "Captured" graph immediately after making a measurement).