Dryer air is warm, not hot. Taking twice as long to dry clothes. Vent is OK, etc. Is the heating element going? What is the part number for the element?
The most likely reason for the unit only getting warm and not hot to dry the clothes properly would be a faulty cycling thermostat WE4M294. If the thermostat is opening too rapidly then it would cause this issue. The part number for the heating element in case it is needed would be part WE11M26.