Hi All,
The special firmware as mentioned in the earlier post released. For those having issue to upgrade the SOHO MK3 device, please help to upgrade the device using the followings firmware :
https://download.peplink.com/firmware/br1ac/fw-max_br1mk2_hotspot_sohomk3-8.1.0s027-build4947.bin
sha1: 816d6c7b70c68a23acee92c92890da6edd227b68
Please report back if firmware upgrade still having issue 