Dolphin appears to now have a feature that detects free space and prevents files from being copied, however Dolphin is unable to actually calculate free space properly and blocks all file transfers to remote filesystems.

1. A cifs fileserver shares data and has plenty of free space. //fileserver/share
2. An intermediate server mounts //fileserver/share at /mnt/remote/fileserver-share
3. My workstation mounts intermediate:/mnt/remote at /mnt/remote

From my system I can df -h /mnt/remote and see the tiny amount of free space on the root volume of intermediate
From my system I can df -h /mnt/remote/fileserver-share and see the ample free space on the actual remote file server share.
I can also df -h /mnt/remote/fileserver-share/some/deep/folder/path and see the same ample free space on the actual file server.

Dolphin does not check the full path and instead only looks at the local mountpoint on my workstation. It assumes there is insufficient space to copy the file when there is actually plenty of space on the remote server. I am unable to copy the file. Doing it manually with cp works fine in a terminal.

There is also no method to disable this feature.

Side Note: Why am I using an intermediate server instead of mounting the file server directly on my workstation? Well it's because so much of Dolphin and KDE is always blocking on disk IO that it effectively renders my entire computer unusable because some background process is hung up on a slow connection and blocks the entire UI while some files are being copied in the background or a slow folder is simply being enumerated. So I am concealing the remote servers behind a mountpoint proxy server so KDE will stop freezing. Having the UI freeze because of high latency or a low bandwidth remote file server is extremely frustrating.