Maybe the rubber belt (if there is one) is slipping and causing a rubber burning smell or maybe a small creature got into your vent and died down inside the dryer and is being roasted or a motor is overheating and smoking. Sometimes it takes a while for a bad smell to clear even if the cause was resolved. Try some of that dryer stuff they add when putting clothes in that comes in zillions of fragrances. My wife often uses that stuff and our garage smells like perfume for hours and hours, They have versions for dryers and for washers or maybe a stronger antiperspirant to keep the clothes fresher.
