[AW-GTS-287A][6.45.1820]Upgrading firmware to the latest version 0002 shows Invalid image

When upgrading AW-GTS-287A firmware from 6.45.1820 to the latest version 0002_20171207_201801014.imgs on web site, it shows "The uploaded firmware image is invalid" as below pictures.
How to solve it?

Upgrading below firmware then upgrading to the latest version 0002_20171207_201801014.imgs on web site solves the problem.
ftp://fae:fae@ftp.vivotek.com/PoESwitch/AW-GTS-287A/AW-GTS-287A_0002_20171207T181339.dat
After upgrading the latest version 0002_20171207_201801014.imgs, firmware version will show 0002.