SQL server backup to CIFS share - syntax issue ?

I am trying to perform an SQL server "built-in" backup (part of a maintenance plan that was working so far) to a file share.

I understand that I have to use UNC in my file path and that the user running the SQL service should have access to the share - as such I have changed the DSQL service user to a domain user.

Checking my logs I see

Failed:(-1073548784) Executing the query "BACKUP DATABASE [model] TO  DISK = N'\\\\172.16.200...." failed with the following error: "Cannot open backup device '\\\\172.16.200.253\\Backup\\SQLDB\\model\\model_backup_2019_11_25_220003_1049249.bak'. Operating system error 67(The network name cannot be found.).
BACKUP DATABASE is terminating abnormally.". Possible failure reasons: Problems with the query, "ResultSet" property not set correctly, parameters not set correctly, or connection not established correctly.

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Seems that it is actually an issue in finding the network share. This is how I have defined my destination :

Isn't that the correct way of doing it ?