sim7600EI hangup / GPIOs held at 1V8

Hi,
I am facing this weird issue with sim7600EI modems:
At random intervals, the modem stops responding to any AT commands of the microcontroller. When this occurs, the following is observed:

  1. Modem GPIO’s look to be pulled HIGH. Modem status pin, network status pin, Modem Tx_1V8 is all pulled high to 1V8 rail.
  2. Modem does not respond to AT commands or to power off/power on signals on the modem power pin. (Timing diagram is followed)
  3. The above is only resolved where there is a physical power cycle of the modem (physical power disconnection)
  4. This looks like something has caused the modem to hang-up and the GPIO’s latch on to 1V8 level.

Has anyone faced any similar issues? any suggestions or a workaround apart from a physical power cycle?