Illustrator Save for Web (Legacy) saving PNG slices as JPG files

Even though I installed the latest Illustrator update this morning (v. 29.5.1), I am still having issues with attempting to export slices as PNG files. The program randomly defaults to a JPG suffix, even though I've selected the PNG format in the drop down on the right (screenshot attached). If I delete the .jpg suffix and replace it with .png, it ends up adding a duplicate .png (.png.png) to the end of the file name. From time to time, it will save MOST of the slices as PNG files, but one of the slice will randomly be saved in a JPG format, which I did not select.

I know that I will be told to delete my preferences file (good luck finding that on my late 2023 MacBook!), but that is such a major pain to have to go back in and change all of my preferences back to ones that make sense to me. Sigh... I will if I have to, but so far nothing else has seemed to fix the problem, even creating a new Illustrator file to see if the glitch was in the file.

Thoughts? Ideas?