Conflict with Polylang

Hi.

There is a conflict with Polylang.

Is not possible to assign other language courses to a created course. No errors in log, simply the association is not saved.

It works if I comment line 1204 of course.php file:
//remove_action( 'save_post', array( $this, 'before_save_curriculum' ), 20 );

I′m using a clean WordPress 4.9.1 installation, LearnPress 2.1.9.4 and Polylang 2.2.7

Thanks