There's gold text "Electronic Sensor" above the start button.
Damp clothes making contact across the sensor bars causes the timer to stall ... so the timer won't stall if there's residue on them preventing completion of the circuit, which will make the cycle shorter, not longer. The clothes will come out damp due to insufficient drying time.
Regards to needing 60+ mins to dry a load, both the auto-dry cycle and timed take comparable amount of time? The load fully dries, it just takes more time than reasonable?
This is the same exhaust duct on which you previously had a dryer? Did it exhibit the same characteristics?
The "swelling" of the flexduct during operation perhaps is a clue confirming there's an exhaust outlet restriction.