I’m doing stress test for a prototype the whole month of December until now. I guess I’m in a different region as yours, but my DASH boards also experienced a couple of disconnections… sometimes in GPRS connections but most of the time in the network registration.
So I learned my lesson to include in the code level my own network recovery… parse returned messages and count ERRORS, after 3 counts call recovery block (disconnect - connect to cloud).
Since in PH there’s still 2G services, I found out via NOVA that most of the GPRS disconnection happens when the board shifted from 3G to 2G… so I forced board to Single Mode UMTS (AT+URAT=2).
Also, watch out for the power supply voltage/current… dipping lower than 4.8 volts affected the process of my board… (no response message received via SystemSerial)… and it caused my code to wait for eternity. So better add your millis() expiration in your send/receive code block to make sure your code recovers from this state.