Network connection Error during calls - Dual SIM - XA2

REPRODUCIBILITY (% or how often): Several times, happens randomly
BUILD ID = OS VERSION (Settings > About product): 4.0.1
HARDWARE (XA2, X10, X10 II, …): XA2
UI LANGUAGE: Eng
REGRESSION: (compared to previous public release: Yes, No, ?): ?

DESCRIPTION:

During calls I get several times a network connection error with a dual SIM phone. I only encountered the problem with one of the two SIMs yet. It happens randomly during the call and my connection gets lost. It is a roaming SIM from a foreign country. Maybe the service provider causes the bug. Are there any ways how I can produce logs to discover the cause for the network connection error?

Having a long phone call with me is under this circumstances are not practicable.