XBee 3 sometimes can't register to LTE-M after exiting sleep with PSM enabled

We have an XBee 3 device in system that is used to communicate to our backend over LTE-M. I have enabled PSM with bit 3 of the DO (device options) register and have enabled pin sleep using the SM (sleep mode) register. In between uses, I put the Xbee to sleep by pulling the D8 pin high.

When the radio needs to be used, I pull D8 back to ground. Most of the time, the device wakes up and responds to the ATAI command with 0x2C, indicating the modem is hibernating as expected and successfully connects to the network.

However, about a third of the time, it instead responds with a status of 0x22, indicating that the modem is registering to the network. It seems to stay in this state indefinitely. I’ve worked around this by issuing a shut down (ATSD) and force reset (ATFR) command to kick it out of this failure mode. This works, but I would prefer to avoid shutting down the XBee if possible. For further context, we are using a hologram SIM in the US and our carriers should support PSM.

Any suggestions on what else to try? I have also played with the ATPA and ATPU timer registers to see if this impacts the behavior I’m seeing, but I could not find any correlation. Thanks!

Please contact Digi Support @technical.support@digi.com

FYI, this was fixed by updating the XBee firmware to 11418 or later