Hi all, I did not find any solution to this online, so I write it down here in case someone has the same issue.
I had to update an old Gallery from 1.7.x to 2.0.2 for MySQL8. It is in constant use since 2018, so many images were added. When trying to update it via MODX Package Management, the procedure got always stuck at “Attempting to preserve files at”. Because there is an image cache inside assets/components/gallery/cache with loooooooooooooots of images to “preserve”.
Removing all files from assets/components/gallery/cache allowed me to install v2.0.2 smoothly.