ECM mode stops working

Running Bullseye on the raspberry-pi 4B 2GB - Setup for ECM mode.

Using the online remote terminal -

After a checking on the device using AT commands as specified here: Cellular Internet Connection in ECM Mode, I get a python error shown in the image:

The reason I am looking at the AT commands is because ECM mode seems to shut down after some time, even if I am sending packets every 3 minutes… That lead me to look at what davidbonn published here: Another ECM Mode question

One problem compounded by another - Help?!

P.S. AT commands work fine, for a while, after a reboot of the entire system.

Are you using both ECM and Sixfab CORE at the same time?
You should be using one.

Which module are you using?

At the beginning I installed sixfab CORE using the install script on the Bullseye OS. Since the connection kept dropping, I started looking at the AT commands.

After I wrote the initial post above, I fell back to the Buster OS and followed the sixfab CORE install script again. Now the connection seems to be stable - It has been running overnight and is still running.

To make sure I understand, are you saying that using the sixfab CORE means that I should not be using any AT commands to “look” at the system? Or, in other words; use the sixfab CORE which sets up the wwan0 connection and “don’t worry” about it?

The module is: LE910C4-NF

You can use AT commands through /dev/ttyUSB3 for your operation with the module, as Sixfab CORE uses /dev/ttyUSB2.
Both ECM and Sixfab CORE establish an internet connection, so you should use either.