Thermostat decreases by a few degrees every few seconds

A while back my kettle was scaled over pretty badly and as a result ended up boiling over several times. I set it to dry it with some desiccant packs, but since then, every time I turn it on, the thermostat readout starts ticking down from whatever my desired temperature by a few degrees every few seconds.

For example, if I turn the kettle on with cold water and set the temperature to 100 degrees Celsius, after about a minute, The set temperature readout (not the reported thermometer reading) willbe down to 90 degrees Celsius. So if I want boiling water, I have to keep turning the knob to the right.

What could be the problem here and how might I go about fixing it?

I've de-scaled the kettle several times since this problem started, and it makes no difference.

The problem seems to be with either the control knob or the thermostat