FTPFS under Haiku is buggy?

[TCH68k]

I have a Linux host with an FTP server running on it and a VirtualBox guest Haiku. I've installed the necessary stuff

pkgman install userland_fs curlftpfs

and i can mount the FTP by

/system/servers/userlandfs_server curlftpfs &
mount -t userlandfs -p 'curlftpfs user:password@192.168.10.100' /mnt/ftp

It works somewhat, but i am constantly getting messages like:

ftpfs: operation ftpfs_open failed because Not supported

and

ftpfs: operation ftpfs_getattr failed because No such file or directory

and if i copy there something

ftpfs: operation ftpfs_flush failed because I/O error

Now, the copied file arrives there all OK, but if i delete a file on the host side, then Haiku thinks the file is still exists and does not exists at the same time:

cp: cannot create regular file '/mnt/ftp/nfsmount': File or Directory already exists
rm: cannot remove '/mnt/ftp/nfsmount': No such file or directory

If i delete it from Haiku, it can be created again. I think this is connected to the flush error.

Did i done something wrong, or it's a known problem?