Safely remove (Unmount) the HDD before you switch off the Router.
Probably it was writing something when you switch the router off.
i think because the router dont understand chinese character, hence it "think" the files are corrupted.. see error below :
Apr 14 21:55:49 kernel: ufsd: utf8 failed to convert '小*.jpg' to unicode. Pos 3, error -5, chars e5 ae 2e
Apr 14 21:55:51 kernel: ufsd: utf8 failed to convert '无与伦比的*.jpg' to unicode. Pos 15, error -5, chars e7 be 2e
Apr 14 21:55:53 kernel: ufsd: utf8 failed to convert '春·*.jpg' to unicode. Pos 5, error -5, chars e6 97 2e
Apr 14 21:55:54 kernel: ufsd: utf8 failed to convert '苏打绿-*.jpg' to unicode. Pos 10, error -5, chars e5 8d 2e
Apr 14 21:55:55 kernel: ufsd: utf8 failed to convert '苏打绿同名*.jpg' to unicode. Pos 15, error -5, chars e4 b8 2e
Apr 14 21:55:56 kernel: ufsd: utf8 failed to convert '陪我*.jpg' to unicode. Pos 6, error -5, chars e6 ad 2e
Apr 14 21:55:58 kernel: ufsd: utf8 failed to convert '蔡*.jpg' to unicode. Pos 3, error -5, chars e4 be 2e
Apr 14 21:55:59 kernel: ufsd: utf8 failed to convert 'J-Top冠军*.jpg' to unicode. Pos 11, error -5, chars e7 b2 2e
Apr 14 21:56:00 kernel: ufsd: utf8 failed to convert 'J9 New + Party *.jpg' to unicode. Pos 15, error -5, chars e7 b2 2e
Apr 14 21:56:03 kernel: ufsd: utf8 failed to convert 'J世纪Jeneration 大牌新曲精*.jpg' to unicode. Pos 33, error -5, chars e9 80 2e
Apr 14 21:56:07 kernel: ufsd: utf8 failed to convert '单身情歌·万人*.jpg' to unicode. Pos 20, error -5, chars e8 88 2e
Apr 14 21:56:08 kernel: ufsd: utf8 failed to convert '唯舞*.jpg' to unicode. Pos 6, error -5, chars e7 8b 2e
Apr 14 21:56:10 kernel: ufsd: utf8 failed to convert '*.jpg' to unicode. Pos 0, error -5, chars e5 9f 2e
Apr 14 21:56:11 kernel: ufsd: utf8 failed to convert '爱的练*.jpg' to unicode. Pos 9, erro
think i will open a case with Asus, not sure if they will read it...