I made an Advanced Custom Field entry for the 'unblock' field to easily switch between true/false. However, it doesn't matter what the setting is on the field (can be true, false, 0, 1) it always unblocks the post/page. I have to delete the custom variable altogether to make it block again.
wp-members-core.php at line 338 doesn't make any sense. You would have to change it to something like this:
$unblock_var = get_post_custom_values('unblock');
if( WPMEM_BLOCK_POSTS == 1 && (!isset(unblock_var) || (isset($unblock_var) && ($unblock_var == "false" || $unblock_var == "0"))) ){ $block = true; }