Hello Peplink Team,
We may have found a firmware bug with versions 8.1.1, 8.1.2 & 8.1.3b1 affecting the cellular connections.
It isn’t easy to reproduce, and we have only seen it so far on the MAX Transit DUO.
The fault that we have been observing happens mostly when the B Slot is set to a Custom APN & then resets back to the A Slot. The A Slot will need to be on Auto APN. What appears to be happening is the A Slot wants to use the B Slots Custom APN.
- If a SIM in the A Slot can use the B Slot APN, then the A Slot SIM will connect.
- If the SIM in the A Slot cannot use the B Slot APN, then the A Slot SIM will fail to connect.
Sometimes the system will get stuck on the B Slot SIM and not switch back to the A Slot. We have observed that when the system is configured to use both SIMs and the B Slot is the prefered slot yet empty (no SIM in Slot B), the modem gets messed up and will not switch back to the A SIM.
This has taken us months to isolate. We thought it may have been the SIMs or the SIM Extenders we use or even the physical device, though we are reasonably confident now that it is a firmware issue that we have been chasing.
The existing related ticket to this is #21020630, where we have updated with fresh diagnostic files for the engineering team to review.
Happy to Help,
Marcus 