EC25E - Occasionally unable to detect ringing/incoming call


We are using EC25-E, firmware revision EC25EFAR08A02M4G on a custom board with a Yocto Linux on it.
Problem we have is sometimes when we call the phone number of the inserted SIM, we hear ringing (on the phone side), but checking for modem status does not indicate an incoming call is coming in and ringing.
Most of the time the modem works time, but the problem happens occasionally and keeps repeating.
Different operators or numbers used does not seem to play a role in this.
Currently using an Austrian A1 card in roaming with various German operators.

Way we perform checks is using: ‘mmcli -m 0 --voice-list-calls’
When the problem occurs, the ringing is happening but modem manager will return No calls were found instead of a call of ringing status.

1 - Any idea why this is happening or what the problem is?
2 - Is the problem potentially due to using modem manager rather than direct commands to the device?
3 - Do you recommend an alternate approach or some alternate commands to be used as a method of obtaining ringing events?


Hi, Can you switch the network to the GSM and test if there is no ringring?

Im not really sure what you mean switch the network to the GSM?

Want to know whether the same problem exists under different network system