Is this Siemens a heat-pump dryer?
Non-reversing dryers are crap... As I've said before, with some items you will get a big "ball" or "Wäschekloß" as BOSCH calls it. They recommend to dry different items in one load... E.g. towels with bedding cloths... No other brand offers only uni-directional dryers so we've decided to never buy a BSHG appliance again...