Apple iOS 14.5 and upwards (so far) has a introduced a bug preventing apple users from uploading or creating files on their local samba drives on the network. The upload will start but eventually fail with an error popup:
The operation couldn't be completed. Operation cancelled
If you have access to the samb configuration file (smb.conf) then you can apply a known workaround. In my instance, my samba is hosted on an Ubuntu machine. Edit the file found at /etc/samba/smb.conf and under the [global] section add the following 2 lines:
[global]
vfs objects = fruit streams_xattr
fruit:nfs_aces = no
Then restart samba
service smbd restart