On my side, I tested if the mount point existed before mounted it:

if (!dbutils.fs.mounts.map(mnt => mnt.mountPoint).contains("/mnt/<directory>"))
  dbutils.fs.mount(
    source = "adl://<datalake_name>.azuredatalakestore.net/<directory>",
    mountPoint = s"/mnt/<directory>",
    extraConfigs = configs)