Applying a stroke colour changes the fill instead

I've noticed a bug where when I create an object, I can't simply apply a stroke to it by selecting a colour from the swatch icon in the control dock. When I select the stroke colour icon and choose a colour it changes the fill colour instead, whereas previosuly a new stroke would be applied with the chosen colour.

In the screenshots below I have a black fill on the rectangle object. I then try to apply a yellow stroke and in the following screenshot, you can see that it changes the fill instead.

In the third screenshot, I have added a stroke by selecting the dropdown menu for the stroke weight then selected the stroke colour icon and chose my colour which should be blue but it changes the fill instead.