RTE always on text mode by default

Can’t really think of a reason for the behaviour, maybe it is just a bug in the theme, of course I can’t say anything specific without knowing the code. But you should be able get around it by making use of the wp_default_editor hook and explicitly set the type of editor you want to show first, which is inside the function with the same name, so wp_default_editor().

function wpse194059_set_wp_default_editor( $editor ) {
  // possible values are: 
  // tinymce - visual mode
  // html - text mode
  return 'tinymce';
}
add_filter( 'wp_default_editor', 'wpse194059_set_wp_default_editor' );