The plugin save the name table wrong when use `` in the name table and this affect the filter function.

When use  

 ...FROM `table_name`  with (``) the filter left to work because wpdatatables query add an additional `` to the query and the filter left to work... because

...FROM `table_name`  WHERE  ``table_name``.`field` ..... <-the plugin put double ```` in the table_name condition. 

So the user must be use  ...FROM table_name  without `` to makes the filter works.

The plugin should be prevent in order to users could use both format with and without `` format.

I hope this help you to fix the problem in the future.

Only have to modify a couple of lines in your code

Regards

Alejandro