The thermal fuse opens when it has been at 91C for several minutes. This is often an airflow issue and I see it all the time. If it takes more than 60 minutes to dry a normal load that points to airflow issues.

There are a few other reasons though and your statement that you cannot control the temp is a clue.

Set it for air dry. If it heats there you probably have an element shorted to ground. To check for continuity put a lead on a element terminal and the other on the metal duct around the element. Repeat for both terminals. If it's heating even in air dry the element may have sagged and be touching the duct or the element frame. This would give you continuity to ground. If the element hasn't actually broken this situation may still pass a continuity test through the element, but is also allowing a path to ground.

If the element is definitely not touching anywhere, you'll need to see if it is being supplied 240v all the time, even in air dry. This would mean your main control has a stuck relay. The element will always get 120v if the motor is running, the control provides the other 120v.