EG25 can't read SIM

I’ve got a Quectel EG25-G that suddenly cannot read the SIM. The modem is installed in a PCengines APU2d, and I’m running an OpenEmbedded Linux build based on Yocto. It worked for me several months ago, and a Sierra Wireless modem inserted in the same card slot is able to read the modem.

These lines from the ModemManager log seem most relevant:

Aug 30 20:26:42 url-000db95362a6 ModemManager[552]: [modem0] couldn’t query SIM slots: QMI protocol error (94): ‘NotSupported’
Aug 30 20:26:42 url-000db95362a6 ModemManager[552]: [modem0] state changed (unknown → locked)
Aug 30 20:26:42 url-000db95362a6 ModemManager[552]: [modem0] modem couldn’t be initialized: Couldn’t check unlock status: QMI operation failed: Illegal SIM/USIM application state
Aug 30 20:26:42 url-000db95362a6 ModemManager[552]: [modem0] state changed (locked → failed)
Aug 30 20:26:42 url-000db95362a6 ModemManager[552]: [modem0] couldn’t open ports during Modem SIM hot swap enabling: Couldn’t get primary port
Aug 30 20:26:42 url-000db95362a6 ModemManager[552]: [modem0] SIM is missing and SIM hot swap is configured, but ports are not opened.

Package revisions are:
ModemManager 1.18.4
libmbim 1.26.2
libqmi 1.30.2

Can anyone suggest where I should start in diagnosing this?

We have been seeing the exact same error.
done 100+ installs using the same ModemManager version, all at once sims seem to bee failing.

other debug information:
on first boot: sim seems to be found and working
it’s only after reboot that the error occurs in our case.

did you manage to fix the issue?

I’ve had no luck yet.

we installed another modem and the issue was resolved.
We assume therefore that the modem is malfunctioning.
How the modem broke in the first place - we don’t know.
if possible, that seems my best advice: try another modem

Yuck. I was afraid of that. How have you been turning off the modem? Do you issue a shutdown command to the modem, or do you kill power to the entire system? I’ve been working on a project in which the system is expected to be an unattended box, just like a router or switch, where battery backup isn’t available, so yanking power is considered normal operation. Perhaps the Quectel isn’t up to dealing with that.

indeed, we didn’t shut down the modem, we shut down the whole device.
And the issue hasn’t been reproduced since the modem has been replaced.
One option we considered for modem malfunctioning: that static somehow killed or damaged the modem during installation. But I suppose that is no option for your setup.

Static seems pretty unlikely in my situation. The modem was installed for several months before this happened, and the relative humidity in my office has been around 60% all summer.