Technical Tip: FortiExtender-311F rebooting after upgrade to v7.4.4

In FortiExtender-311F, when the upgrade process from v7.2. x to v7.4.4 is done, it is under a rebooting loop state, and actions like turning it off or doing a factory reset did not help: 

End modem firmware upgrade
please wait 5s for modem resetting.......
GPIO reset modem...
.. bring modem down ..
done
.. bring modem up...
done
please wait 5s for modem boot up!
******* Start modem firmware upgrade
******* create temporary file
******* decrpt the modem firmware
Archive: /tmp/firmware/FW/EM160RGLAUR02A08M4G_01.001.01.001.zip
  inflating: contents.xml
  inflating: md5.txt
   creating: update/
  inflating: update/abl.elf
  inflating: update/aop.mbn
  inflating: update/devcfg.mbn
   creating: update/firehose/
  inflating: update/firehose/partition_complete_p4K_b256K.mbn
  inflating: update/firehose/patch_p4K_b256K.xml
  inflating: update/firehose/prog_firehose_sdx24.mbn
  inflating: update/firehose/rawprogram_nand_p4K_b256K_update.xml
  inflating: update/hyp.mbn
  inflating: update/multi_image.mbn
  inflating: update/NON-HLOS.ubi
  inflating: update/partition.mbn
  inflating: update/partition_nand.xml
  inflating: update/sbl1.mbn
  inflating: update/sdxpoorwills-boot.img
  inflating: update/sdxpoorwills-recoveryfs.ubi
  inflating: update/sdxpoorwills-sysfs.ubi
  inflating: update/sdxpoorwills-usrfs.ubifs
  inflating: update/sec.dat
  inflating: update/tools.fv
  inflating: update/tz.mbn
  inflating: update/uefi.elf
  inflating: update/usrdata.ubi
  inflating: update/xbl_cfg.elf
[000.000]: Version: QFirehose_Linux_Android_V1.4.8
[000.000]: Builded: Apr 23 2024 22:33:07
[000.000]: Find md5 check file </tmp/force_upgrade/md5.txt>
[000.001]: md5 checking: /tmp/force_upgrade/contents.xml pass
[000.004]: md5 checking: /tmp/force_upgrade/update/abl.elf pass
[000.008]: md5 checking: /tmp/force_upgrade/update/aop.mbn pass
[000.009]: md5 checking: /tmp/force_upgrade/update/devcfg.mbn pass
[000.009]: md5 checking: /tmp/force_upgrade/update/firehose/partition_complete_p 4K_b256K.mbn pass
[000.009]: md5 checking: /tmp/force_upgrade/update/firehose/patch_p4K_b256K.xml pass
[000.016]: md5 checking: /tmp/force_upgrade/update/firehose/prog_firehose_sdx24. mbn pass
[000.016]: md5 checking: /tmp/force_upgrade/update/firehose/rawprogram_nand_p4K_ b256K_update.xml pass
[000.018]: md5 checking: /tmp/force_upgrade/update/hyp.mbn pass
[000.019]: md5 checking: /tmp/force_upgrade/update/multi_image.mbn pass
[001.173]: md5 checking: /tmp/force_upgrade/update/NON-HLOS.ubi pass
[001.174]: md5 checking: /tmp/force_upgrade/update/partition.mbn pass
[001.174]: md5 checking: /tmp/force_upgrade/update/partition_nand.xml pass
[001.188]: md5 checking: /tmp/force_upgrade/update/sbl1.mbn pass
[001.383]: md5 checking: /tmp/force_upgrade/update/sdxpoorwills-boot.img pass
[001.793]: md5 checking: /tmp/force_upgrade/update/sdxpoorwills-recoveryfs.ubi p **bleep**
[003.047]: md5 checking: /tmp/force_upgrade/update/sdxpoorwills-sysfs.ubi pass
[003.125]: md5 checking: /tmp/force_upgrade/update/sdxpoorwills-usrfs.ubifs pass
[003.125]: md5 checking: /tmp/force_upgrade/update/sec.dat pass
[003.135]: md5 checking: /tmp/force_upgrade/update/tools.fv pass
[003.157]: md5 checking: /tmp/force_upgrade/update/tz.mbn pass
[003.189]: md5 checking: /tmp/force_upgrade/update/uefi.elf pass
[003.282]: md5 checking: /tmp/force_upgrade/update/usrdata.ubi pass
[003.283]: md5 checking: /tmp/force_upgrade/update/xbl_cfg.elf pass
[003.283]: Totals checking 24 files md5 value, 0 file fail!
[003.284]: Quectel module not found
[003.284]: qfirehose_src/qfirehose.c main 346 fail
End modem firmware upgrade
please wait 5s for modem resetting.......
GPIO reset modem...
.. bring modem down ..
done
.. bring modem up...
done

To fix or avoid this issue, install the v7.6.1 and upgrade the modem firmware to FEM_EM160-24.1.1-build0002.