Why incoming calls from the GSM module do not work correctly on Yeastar MyPBX U100 ?

Question

Asterisk

ACT - Yeastar MyPBX U100, 2 gsm channels + 1 sip number are installed, calls to all numbers are collected on 1 IRV group.
Order:
1) greeting (own record)
2) 10 seconds to choose additional. numbers
3) switching to a group of 3 internal numbers, calling in turn, if no one has picked up - again to point 1.
Problem: if you call GSM numbers, the default greeting is turned on, then our greeting, after which it calls 1- th number from the group of seconds 40 instead of the declared 7-10 and then reset. If If you call a city sip number - the scheme works as it should - everything is ok.
ps Landline numbers are attached to sim cards, they call landlines, the operator is Megafon. If if you interrupt the call to the SIM card without waiting for the operator's response - the second one (an empty call) arrives at the PBX, pick up the phone - silence.