Dual Simm option: Under what circumstances does the unit switch over from the primary to the secondary simm and when does it go back to the primary simm?. Also, what is the time delay when switching over?
The SIM card switches only on specified events (e.g., low signal, no network, etc.). That is to say it will never switch from primary to secondary SIM unless a SIM switch rule(s) is specified. More information on that here.
Also, I would suggest asking questions in Teltonika's Crowd Support forum. You are more liable to get an answer there: https://community.teltonika.lt/