DIAGNOSIS: That's by design, unfortunately. The lint filter on this model is notoriously inefficient, especially with finer lint from synthetics. A lot of lint bypasses it and gets into the blower housing and vent.
FIX: Regular, thorough cleaning of the entire system is key. Clean the filter itself with warm water monthly to remove invisible residue. More importantly, you need to clean out the lint trap cavity (the slot the filter goes into). Use a vacuum hose attachment or a special long lint brush designed for dryers to get deep in there.
IF THAT DIDN'T WORK: Check the seal around the lint filter opening. If it's torn or missing, air (and lint) will bypass the filter entirely. It's a replaceable part.
HEADS UP: The lint that gets past the filter is what clogs up the internal ductwork and causes the "takes forever to dry" problem. If you're seeing a lot of lint in the drum, you should also check and clean the external vent line.