I thought I would post this here, in case anyone come across the same issue. I'm using
yarpp_related_exist($args,$id) to check if there are related 'products', which is a Custom Post Type. However it was throwing an error:
Missing argument 2 for YARPP_Cache_Bypass::begin_yarpp_time()
This is called in class-core.php on line 1032 (Version 4.0.5 of YARPP & Version 3.5.1 of WordPress). Simply change line 1032 from:
$this->active_cache->begin_yarpp_time($reference_ID); // get ready for YARPP TIME!
$this->active_cache->begin_yarpp_time($reference_ID, $args); // get ready for YARPP TIME!
Hope this helps, just remember this is a core file, so updating the plugin will remove this 'fix'.