Charge Plugin - Stripe payments occasionally not being received in craft
At first glance I cannot tell you why your plugin runs intermittently.
But if your plugin is interacting with Charge, there are some log functions you can use that may be helpful. 

craft()-&gt;charge_log-&gt;email("yada yada");
craft()-&gt;charge_log-&gt;note("yada yada");
craft()-&gt;charge_log-&gt;error("yada yada");