I’ll just add my two-pence worth on the use of Samba - I’d recommend moving to autofs. See Mounting network shares with autofs (alternative to fstab).
In my experience autofs is much more reliable when using a Windows platform serving the media files with some version of Samba (this may not of course be your particular use case).
Of course the logs may show the reason, but I have experienced behaviours which are unpredicatbly subject to change on the part of MS when updates are applied to the serving Windows platform.
Also note these posts - Mounting network shares with autofs (alternative to fstab) - #85 by thechrisgregory
If you want to stick with Samba I’d recommend using SMB v3 and do this by adding a network location, specifying the server name but no shares - i.e. specify your login information and save it.
This approach should then give an additional option in the ‘Browse for Location’ of smb://server