We appreciate you taking the time to share your experience with us, but we apologize for the trouble you've had. We understand that service was out for repairs, but that these concerns don't seem to be resolved. While it can be normal for the vent to become slightly discolored, there should not be a build up of clothing fibers forming on it. The metal itself cannot melt from dryer temperatures. If this build-up is occuring, it is usually a sign that the airflow in the dryer's exhaust system is being restricted, or that fabrics may be drying on too high of a heat setting. We'd recommend sorting fabrics into like loads, and checking fabric care labels to determine the right heat setting. From there, we'd also check to ensure the venting material being used is either rigid, or semi-rigid, metal ductwork as flexible foil type venting will restrict the airflow. Then, this exhaust system should be checked and cleaned routinely (roughly every 12-18 months) to ensure it is not blocked/clogged or kinked/crushed. If this doesn't help, please contact our Customer Support at 800-552-5475 (Monday to Friday; 8:30am – 4:00pm Central Standard Time) so we can better assist.