M66 modem: CME ERROR: SIM not inserted

Dear all,
i’m driving a M66 modem module on a custom board.
I can connect and establish PPP connections successfully but sometimes i encounter this problem: when the connection drops and the PPP firmware stack is deinitialized, i close the call by using the command:

AT command:  ATH0

AT response: ATH0OK

but when i try to restart the procedure with a new call:

AT command:  ATDT *99***1#

AT response: ATDT *99***1#+CME ERROR: SIM not inserted

So i can go on and i must power down the module and restart all the procedure.

Thank in advance for your help guys.

It seems that the sim card dropped. It is recommended to query the state of sim card and registration before ppp dialing.
Please check the sim card holder is connected and soldering is ok.
If ok, check the antenna and power line are close to sim card holder, keep the antenna and power line is far away from sim card.

Thank you Aaron,
as i tried to explain in my post, the board is always in the same position (on my desk) with no sort of mechanical stresses which can move the sim.
The board can connect and keep a webscoket for many hours which suggests that the card holder and soldering are OK.
The problem is quite weird because it involves the sequence of commands so the internal states of the modem.
Are the geometrical constraints for the antenna and powerline distances from the sim card?

Could you please tell me more information? Including region,company name, module, issue description(AT sequence). We will assign to coresponding region FAE to support this case.

Sure. Can you leave me your mail?

Please fill the information on the website.The link is https://www.quectel.com/support/technical.htm