I think I found another bug:
I added a few images to a post, previewed the changes and synced the website.
I really thought that everything went fine but when I restarted my computer at a later time and opened Publii again I saw that the images weren’t visible anymore in the post. Instead of showing the images, icons are shown that images can’t be found.
The images were added with the WYSIWYG-editor and I used the options Insert image and Insert gallery.
(I also belief that I synced the website (and verified the changes) but when I look online I also don’t see the images.)
Let me know If I have to test anything!