EC200T PPP disconnect issue

Hello, We are using EC200T module over USB with our MCU. We are able to establish PPP connection and perform data exchange with our servers successfully. However, at few locations we observe that although the PPP connection is working okay as per the MCU PPP stack, we find that data transfer is stopped. When we disconnect and reconnect PPP, data is again through and after a while the same condition repeats.
We are using usbmodem port for the PPP, and while monitoring the module via usbat port, we find that whenever this happens the usbat port receives the following notifications-

+CFUN: 1





We suspect that the modem’s PPP connection gets reset or some other condition happens which causes the PPP to stop working.
Our observation is also that if the data volume is high (600~1kbytes), then the frequency of this happening is more.
What could be the cause of this behaviour and how to resolve this?

Please check your sim connection, you can see from the log that the sim card has been reconnecting

As you can check from the log I shared, the modem also outputs a RDY notification, which indicates that the modem is rebooting, and hence the subsequent messages in the log.
We need to analyze the issue as to why it is rebooting.
I do have one observation. The problem is happening with our boards having EC20 modules, whereas EC200T modules are working fine. The board is identical except for the module itself. So, we are facing issues wherever we are using EC20, but when replace it with EC200T it works fine, without issues.

Are there any known issues with EC20?