Need help - wrong module behaviour

Q24CL module problem.
With newer OS versions we do not get good GPRS behaviour. Since 6.57b module restarts spontaneously after 2-4 hours of work and consumes more money if compared by billing.
OS 6.57b works very good but with some new SIM it is not OK with Data Call. After CONNECT it hangs and restarts after 3-5 seconds. This behaviour comes with every OS version till 6.57e.
Now we need help to resolve this problem? Is there is a way to avoid problems with certain SIM and work with 6.57b which is very good? Or a way of getting GPRS to work as expected? Or something else?

Is this with your own custom application in the module?

When working with GPRS - yes - a custom OpenAT application.
But when we test data call a bug appears not regarding if there is application in module.

Also we found that newer versions of OS (since 6.57b or 6.57e) work worse not only with GPRS but with data calls of all kind on every type of SIM - it can reload spontaneously during data call.
Older version (we test 6.57b) works MUCH better with GPRS and data calls. But it hangs on CONNECT on a certain type of SIM.

I will try to open a topic in Bugs section of this forum.