Sometimes not sending e-mails

Hi,

This plugin never failed but as of lately it sometimes fails to send out e-mails after an order is placed. Both the buyer and us (store owner) should get an e-mail but as I said, sometimes the e-mails are not sent. This makes us miss the orders as well as our customer don’t get the confirmation of order e-mails which is not good at all. Please, help!

The page I need help with: [log in to see the link]