The log file needs to have a truncation happen instead of a shrink, truncations occur after a log backup, for a database with Recovery Mode set to Full it is always recommended to take regular backups otherwise the file will keep getting larger.
Check if a database backup is being done in compliance with the maintenance plan in SQL which will truncate the log file upon completion. If this is not being done then perform a backup at least once so that the log file will be truncated down to a manageable size.