SIM Switch should only be initiated by the SIM Switch service. This service configuration can be found by navigating to Network → Mobile → SIM Switch. Make sure it’s disabled for SIM1 and SIM2.
If that does not help, please wait for the issue to replicate, then navigate to System → Administration → Troubleshoot, open the system log, and paste the past few minutes of the logs in your next comment. This may give us a hint of what could be causing the issue. It may also be related to the other issues you’re facing.