If I go to any dialogue box that has a 'preview' option, the effect is applied as soon as the box is checked. If I then click 'cancel' the effect is still applied. Altering the parameters applies the new value to the previously applied value.

For example, I draw and box and open the Scale options. With 'preview' selected, I change the value from 100% to 200% and then to 150%. The box is scaled to 350% in total.

Also, the Recolour Artwork box will only allow me to change a colour once. Again, applying the change instantly even if I choose 'Cancel'.

This doesn't happen to a newly created document. But if I copy anything from a document where it is happening into a new one it will start to happen.

MacOS 10.14.6
Ilustrator 24