Hi Jeff,
Thanks a lot for your attention and very effective assistance. You are right that there is no appropriate processing of SIP SUBSCRIBE requests. These requests are sent, for example, by Snom IP Phones (used as agent extensions). I really didn't expect it and didn't notice their receiving in trace files.
Although I don't think that it is a serious reason for BSOD crashing, I agree with you that, first of all, it is worth handling SUBSCRIBE messages correctly.
Best regards,
Boris