I'm trying to export products from Magento 18.104.22.168 but when I go to the following location, it just comes with a 500 page error straight away.
System > Import / Export > Dataflow - Profiles
I checked the logs and it has been narrowed down to this:
PHP Fatal error: Class 'Unserialize_Reader_ArrKey' not found in magento/lib/Unserialize/Reader/Arr.php on line 88
How can I fix this? It looks like a patch might not of been applied properly or something.