Problem with SIM registration on some ports.

Good day. We have a problem.

Periodically SIM loses registration. It happening with various SIM's of various mobile operators. Today we noticed that problem again and captured AT command log.
If we will plug that SIM into another port, it will work normally.
We have 2 non-working ports already, today was the 3rd one. And these ports are on various GSM cards.

device: VS-2120-44G
Software Version: 2.1.3
Hardware Version: Date 2012-11-09 FPGA 11 Hardware 00

Hi, please give me remote access, I'll help you to figure it out.

Good day, Michael. How can I communicate with you?