Authorize.net SIM double charges

I've been running ZC for a while with A.net's AIM module without any problems. After upgrading to 1.3.9f (from 1.3.8), I decided to use the SIM module for better PCI compliance. Every so often however, a purchase results in a customer's credit card being charged multiple times. There is no pattern to when this happens, and nothing discernible about the user's interaction with ZC. So far it has happened about once every 20-40 transactions.

I've read through past A.net double charge threads, but am yet to encounter a solution.

There are no addons in this installation.

I did enable DB & file logging for SIM. For the most recent occurrence of this problem, ZC logged multiple communications with A.net (i.e., multiple log files), but only recorded a single entry in the authorizenet table.

DrByte - Any ideas/suggestions?

zg1:

I did enable DB & file logging for SIM. For the most recent occurrence of this problem, ZC logged multiple communications with A.net (i.e., multiple log files), but only recorded a single entry in the authorizenet table.
That looks like the customer has clicked the submit button multiple times, either because the button isn't being disabled by the javascript (maybe they've disabled their javascript in their browser?), or they've used their Back button and submitted again after being redirected?

DrByte:

That looks like the customer has clicked the submit button multiple times, either because the button isn't being disabled by the javascript (maybe they've disabled their javascript in their browser?), or they've used their Back button and submitted again after being redirected?

Wouldn't that have resulted in the transaction having been posted multiple times into ZC's authorizenet table?

No. The emails and database logging would only happen after the customer returns from Authnet. ANd, if they've clicked "again", then only the second click will successfully return the customer to the store. The first click is abandoned, and there's no way to control anything about it once they click a second time. That's why the button is disabled on first click.