Yes, getting to the right person at SIMCom took longer than we hoped.
Nevertheless, we might have a solution for our problem (stress-tests currently running).
SIMCom is unclear as to why the previous batch did not have this issue, but they suggest that the trace width at the VBAT “line” to the SIM7020G modem is too narrow (0.254 instead of 1 mm) and can limit the current provided when modem is actively using the LTE antenna.
So, currently bypassing this VBAT trace (except for the reference design’s capacitors and TVS) and connecting the VBAT pins straight to the 3.6V battery.
We’ll see next monday if all our testdevices are still up and running.