I am currently testing LTE and GNSS functionality using the M5Stack U137 modem.

While attempting to reduce power consumption by enabling PSM (Power Saving Mode), the modem consistently resets immediately after entering PSM, causing PSM to be exited unexpectedly.

I would like to ask whether any additional configuration or specific settings are required to ensure stable operation in PSM mode on the U137 module.

Below are the AT command sequences I sent and the corresponding log records for reference.

09:32:20.651 << +CPSMSTATUS: "ENTER PSM"
09:32:24.457 << RDY
09:32:25.021 << SMS Ready
09:32:26.478 << +CPSMSTATUS: "EXIT PSM"