Hi,
since there was no answer on sending my RMS-links to you, I proceeded to test and found out:
...that the issue (after an "ubus call sim change" sim2 shows "disconnected" for ever, or even more sim2 shows no provider and no dB-antenna power) is NOT, if sim1 is not inserted. So everything is fine if sim1 is missing.
Just if the sim1-card is inserted AND if this card is empty (it is a typical data-prepaid-card from https://prepaid-global.com/ or so) then the modem (or whatever) is corrupted and sim2 does also mo more work.
So an empty data-prepaid-sim-card seems somehow corrupting something.
Unfortunately only a reboot helps to get sim2 working (a modem-reboot does NOT help).
This below is the content in log, when modem switches to sim2 (after sim1 was not able to connect since data was empty):
Mon Jan 23 17:19:16 2023 daemon.info mobifd: [gsm.modem0] Config reload initiated
Mon Jan 23 17:19:17 2023 daemon.info mobifd: [gsm.modem0] Failed to get SIM PIN state
Mon Jan 23 17:19:17 2023 daemon.info mobifd: [gsm.modem0] Reloading modem
Mon Jan 23 17:19:28 2023 daemon.info mobifd: [gsm.modem0] Init "ue usage" modem reboot prevention triggered. Settings likely not set
Mon Jan 23 17:19:30 2023 daemon.info mobifd: [gsm.modem0] SMS storage: me
Mon Jan 23 17:19:30 2023 daemon.info mobifd: [gsm.modem0] APN 'IMS' isn't prepared for PDP 2, preparing it
Mon Jan 23 17:19:31 2023 daemon.info mobifd: [gsm.modem0] APN 'IMS' was successfully prepared for PDP 2
Mon Jan 23 17:19:31 2023 daemon.info mobifd: [gsm.modem0] APN 'web.vodafone.de' isn't prepared for PDP 1, preparing it
Mon Jan 23 17:19:32 2023 daemon.info mobifd: [gsm.modem0] APN 'web.vodafone.de' was successfully prepared for PDP 1
Mon Jan 23 17:19:32 2023 daemon.info mobifd: [gsm.modem0] Attempting to establish connection to operator with 5 seconds of timeout
Mon Jan 23 17:19:32 2023 daemon.info mobifd: [gsm.modem0] Scanning operators. Modem will not respond for a while
Mon Jan 23 17:19:32 2023 daemon.err mobifd: [gsm.modem0] Failed to scan operators
Mon Jan 23 17:19:32 2023 daemon.err mobifd: [gsm.modem0] No valid operators found
Mon Jan 23 17:19:35 2023 kern.info kernel: Changing to SIM2: unable to establish data connection
Mon Jan 23 17:19:37 2023 daemon.notice wpa_supplicant[4678]: wlan0: WPA: Group rekeying completed with 3c:a6:2f:5e:6b:67 [GTK=CCMP]
Mon Jan 23 17:19:37 2023 daemon.info mobifd: [gsm.modem0] Attempting to establish connection to operator with 10 seconds of timeout
Mon Jan 23 17:19:37 2023 daemon.info mobifd: [gsm.modem0] Scanning operators. Modem will not respond for a while
Mon Jan 23 17:19:37 2023 daemon.err mobifd: [gsm.modem0] Failed to scan operators
Mon Jan 23 17:19:37 2023 daemon.err mobifd: [gsm.modem0] No valid operators found
Mon Jan 23 17:19:47 2023 daemon.info mobifd: [gsm.modem0] Attempting to establish connection to operator with 15 seconds of timeout
Mon Jan 23 17:19:47 2023 daemon.info mobifd: [gsm.modem0] Scanning operators. Modem will not respond for a while
Mon Jan 23 17:19:47 2023 daemon.err mobifd: [gsm.modem0] Failed to scan operators
Mon Jan 23 17:19:47 2023 daemon.err mobifd: [gsm.modem0] No valid operators found
Mon Jan 23 17:20:02 2023 daemon.info mobifd: [gsm.modem0] Attempting to establish connection to operator with 30 seconds of timeout
Mon Jan 23 17:20:02 2023 daemon.info mobifd: [gsm.modem0] Scanning operators. Modem will not respond for a while