Preview is all of a sudden changing images to .png

my workflow is I open a .jpg image contact sheet, drag over a selection, edit , copy , new from clipboard and name the image -> new image is now new_image.jpg.

Now , they are automatically .png when I go to rename the copy - Preview is changing the .jpg to .png after the copy.

I want them to stay .jpg - like the original.

I haven't made any OS changes or the like and cannot figure out whats changed.

Apple tech support says thats expected behavior - Preview is suppose to save as .png. They I ask, so what was it not doing that the past 2 years ive been doing this.

Is there a way to get it back to .jpg? Tks.