Did you try "systemctl enable storage-recordings.mount"
Assuming you r doing it this way
[Unit]
Description=cifs mount script
Requires=network-online.service
After=network-online.service
Before=kodi.service
[Mount]
What=//192.168.178.3/TVrecordings
Where=/storage/recordings
Options=username=tv,password=xxx,rw
Type=cifs
[Install]
WantedBy=multi-user.target
Save it in "system.d" as "storage-recordings.mount"
Create a folder in storage name it "recordings"
enable with "systemctl enable storage-recordings.mount"
Might need a restart after enable..
Can you access both folders manually from both machines?
can you access //192.168.178.3/TVrecordings from your Odroid?
In LE 8.1 smb changed a lot and you may need to set it up forcing SMB1 in kodi system settings services...enter the password and save for that path...
So if you add it as a source in file manager you can access //192.168.178.3/TVrecordings
Not sure if I can help you anymore then sorry
Basically if you can see a folder from Libreelec on your network...you can mount it..
Otherwise someone more technical might help you..
I never managed to mount more the 1 source to the same folder...that's when I got errors similar to yours..
Does your server still support SMB1 protocol?
If not add the "vers=2.0" option.
To the other options.
mount -t cifs -o vers=2.0,username=tv,...
or
Options=vers=2.0,username=xxx,...
That's why I asked if you can access your network share from file manager in kodi....could be a SMB issue....what version of LE are you running?
Error changes from Permission deniedto Invalid argument. Looks like the server only speaks SMB1.
Sorry, no further idea beside the obvious wrong name or password. Maybe you can try smbclient to check the access.
Not sure what OS is your folder on?Is it on your Mac or a windows PC?
As you are on LE 8.0.2...If it is a windows PC go to Control Panel...Programs...Turn Windows Features On Or Off and make sure SMB1 is installed...Give permissions to the folder to Everyone as RW..go to Local Policies, Security Options and scroll down to “Network access: Let Everyone permissions apply to anonymous users”. Set this to “Enabled”.Now see if you can browse to your folder from LE trough File manager in Kodi..
If you r on Mac see here..
At least you ll know if it is a network issue between your Odroid and Server..
Also you don't have to add vers=2.0 if on 8.0.2...
no clue,
tried everything .... hopefully sometimes it will work 
Well just tryed to mount an hdd to libreelec from a windows 10pc with LE 8.1.0...smb set to None and it's working fine...
I m still not sure if you can browse from filemanager to your network share?
Or maybe show us the steps you r taking to mount ...
no clue,
tried everything .... hopefully sometimes it will work
I've the exact same symptoms as you do, did you ever solve this problem?
