It may be.
I’ve found some other rules. I can resize and create a thumbnail for an image 1252×100 px. But for a picture 2480×1400 px it doesn’t do anything.
Another thing that files and folders within photo-gallery have permission 700 (folders) and 600 (files).
In my wp-config I have
define( ‘FS_CHMOD_DIR’, ( 0755 & ~ umask() ) );
define( ‘FS_CHMOD_FILE’, ( 0644 & ~ umask() ) );