A while back, I had a problem with my dryer that when serviced, a flexible attachments was installed. It looked like metal but wasn't and the air flow was somewhat restricted as it was not a direct path to the outside of my condo.

I had to have it redone and a rigid metal attacment was installed with metal taping. I had a vent hole installed as it was a much shorter route to the outside world. No problems since.

BTW - if one's clothes are damp after drying, it is a very good indication that vent hole is clogged and requires immediate attention. Unfortuately, I'm not too bright as it blew the dryers fuses twice. :(

I aslo clean my dryer's lint trap after each use.