Export incredibly slow on Mac Pro 2013 and latest OS

Hello there,

I had stopped photographing for some months. I am now getting back with new DNG files from a recently second hand purchased Leica X2.

My software was tailored to export different versions of the file at once and it took a few seconds per photos.

It is now turning almost forever, with the delay growing from several minutes to several hours by the time I am writing these lines.

Can someone here please help me understand what is going on!?

I am really puzzled. C1 never did this to me in the past and I have been using this software for years now...