try again with these changes https://github.com/openwrt/openwrt/pull/626
please consider money support to my webmoney WMZ purse: Z290111431046 (PP,Bitcoin and others are not an option)
write and post MT7620 devices you use, their exact revision and wikidevi links to these devices
if there is enough interest (and support) i will try to get 4-5 most popular devices and continue to work on stabilizing wifi drivers