In FSE editor (here editing the footer template), new section container CSS is not included (on the canvas you can clearly see that container doesn’t have auto margins):
This is some strange behaviour as we use Gutenberg’s native function to import these styles in the Site Editor. These styles are not generated in Cwicly at any stage, and the same file is used on the frontend.
Have you emptied caches on your browser?
I switched my site to Litespeed Web ADC Load Balancer, but I had not installed LSCache plugin yet. So I guess some stuff had been cached at server level with no way to clean it. After setting up LSCache, I purged everything again and the default CSS is back to normal