If adding SAMBA shares via the UI isn't working correctly, you can tweak mount options of SAMBA shares via the /etc/smbmounts.conf file.
The format is as follows:
id;smbshare;user;password;mount-options
e.g.
1;\\192.168.99.1\music;music;music;vers=2
id is just any unique ID you want to give to this share. You can leave options empty if no specific mount options are needed.
After editing the file, run
/opt/hifiberry/bin/mount-smb.sh