after an overwrite with the loop location set, reset the next sample to be read

libs/ardour/disk_reader.cc

@@ -736,6 +736,10 @@ DiskReader::overwrite_existing_audio ()
 		}
 	}
 
+	if (_loop_location) {
+		file_sample[DataType::AUDIO] = start;
+	}
+
 	return ret;
 }