RC7611 reports ERROR when changing KSLEEP modes (sometimes)

For using the MBPL SDK to upgrade FW:

For firmware over the air, you can see here:
https://doc.airvantage.net/fota/howto/gettingstarted/

For firmware upgrade locally by XMODEM, you can see the command +WFWUPD in AT command user guide:
https://source.sierrawireless.com/resources/airprime/software/rc76xx-at-command-reference-guide/#sthash.9S1uazwr.dpbs