Problem with GdImage no-image.png

Hi,

I have a problem when uploading no-image.png with file manager. I recently switched from contao 3.4.5 to contao 3.5. On the old version, I didn't have any problem with the image file, when I post something, default image "no-image.png" would be pulled from assets/images. But now I have a problem that contao is adding subfolders 1-9 and a-einside images folder and adding some random numbers to the image file name. So I get this warning and the image is not loaded:

Warning: imagepng(/var/www/html/assets/images/3/no-image-8731b803.png): failed to open stream: No such file or directory in system/modules/core/library/Contao/GdImage.php on line 196

OR

Warning: mime_content_type(/var/www/html/assets/images/e/no-image-99378a1e.png): failed to open stream: No such file or directory in system/modules/core/library/Contao/GdImage.php on line 192

Can I prevent this adding of subfolders and picture renaming?

Thanks

TL:DR

Files are not being copied from files/upload/post to assets/images

The files are not copied. The images would be created there. Looks like a permission issue.