Please post screenshots of the Syncthing Web GUI, including the ignore patterns. The folder local state should change once the patterns have been applied.
The pattern *._ actually tells Syncthing “ignore everything that ends with a dot followed by an underscore”. So if you have a file such as “filename._” it’d work fine.
Instead, use the following pattern:
._*
It says “ignore everything that begins with a dot followed by an underscore”.