I am making extensive use of Direct for both stores and arbitary function calls. I have noticed on occasion the callback functions of ad-hoc calls are not fired upon successful Direct-server interaction.
Unfortunately I do not have a cast iron fault-case. But have pin pointed the problem to the callback definition. After inspection of the transactions within the Ext.Direct singleton, I have noted that in some cases the cb property of the transaction is undefined. Furthermore if I manually set it after calling the function, it works!
I'd be grateful if anyone could elaborate further, direct further debug or alert if the work-around is a cardinal sin.
// In some circumstances the callback is not registered, although the transaction
// is conducted successfully
Ext.Direct.getTransaction(Ext.Direct.TID).cb = console.info;
// this manual registration following the Direct call successfully makes
// the callback fire, when the transaction completes...