One more problem found: from time to time I get the message for the SIM I switched to as "empty string operator name, MNC: 0 and MCC: 0". The message is displayed about one second before having the GSM signal icon in place, thus I assume you are checking these parameters to early for the second SIM.

And finally I think I found the reason sim-switcher script is not always working as scheduled job, despite what I thought earlier that this was solved by increasing the delay between down and up. When running in this way (e.g. through Alarmed), the calls for switching the SIMs might be performed with the phone in some sleep or idle state and thus first switch succeed and switching back fails (due to "Calls not allowed" error). This highly depends on how many hours the phone was in idle state, so that is the explanation sometimes the script succeeded and sometimes fails and then I had to run killall csd to be able to switch back. In this situation, reactivate is not working.

Wondering if you have some idea how to wake up the phone in some state similar with the one when using the script through application icon and put that code in the script? I hope this makes sense.