I edited your file and now everything works as expected.
Here is what I did to achieve the desired result:
-
Button.
I added different text properties (Default Text and Hover Text) to the button variants text layers and overridden the values of each component instance variant. -
Card.
I renamed the text layer to “Caption”, copied this text layer and added it hidden in the Default variant. Then I overridden the value into the component instance.
To override the color, I added an “Overlay” layer to each card variant and set the opacity to 0 in the Default variant. Then I overridden the color into the component instance.