The number one reason for this problem is the lint filter. A build up there can result in lint clinging to the seal on the door, preventing proper closing, or lint bypassing the filter and building up in the exaust tube or around any sensors.
With the Electrolux there is a special sensor that decides when a load is dry enough.
Another possibility is a buildup of lime in the drum. This blocks the action of the sensor. This can be helped by wiping the inside of the drum several times with vinigar. DO NOT use abrasives or scratchers.
The third most likely is that the washer is not spinning out enough of the water or a load that is too large. This results in a situation beyond the limits of the sensor. Manuals library does have a pdf file for this dryer. Page 9 gives several troubleshooting tips.

I suspect either the lint trap is completely stopped up or the dryer hose is clogged up. From the limited information I have to go on I doubt it is a thermal fuse.