UBB.threads PHP Forum Software Community Forums UBB.threads Installation and Upgrade Support File Manager problems

Thanks for helping!

I control the server and hence the PHP ini.
The allow_uploads is ON, the max. upload site 32M.

The upload test files are around 10 KB only.
I have the "inline images" option turned off.

"Old" attachments (uploaded with the old forum and migrated by me to the new forum) work. It's only the new file manager fails to upload files.