editing master component wrecks all instance overrides

I have a component which is basically an image with a mask and a gradient with transparency on top.

I had a bunch of instances in which I changed the image.

Then I updated the master component by adding a solid colour background under the whole thing...

Hell breaks loose and all my overrides are reset to the original image despite the fact that I haven't touched the image of the master component.

This is the opposite of what components should be about!

what's the point of having components if I have to manually redo every single instance after I edit the master component?

I've been able to fix the issue on the file where the shared library is by undoing everything but other files using the shared library are now messed up and won't get the overrides back.

Is there a PROPER way of editing a master component so that the overrides of all the instances are not instantly reset? It defeats the point of components.