Was getting a lot of brown streaks on white laundry two or three per garment (about 1" long with tapered ends, tough to get off -think it might be scorch. cleaned out the exhaust some months ago and streaks stopped but now are coming back so am cleaning the exhaust again. All my drying is done on gentle cycle. Wondering if there is some other cause of this problem that you might know about. Hopefully, sylvie culbertson
If a Whirlpool dryer, you probably have a worn gasket at the back of the drum.
If so you can order one here, it comes as a kit with high temperature glue. You will also need to clean the back panel with comet cleanser.