Coolpad dazen 1 OTA update failed error state 7.

Hello..
I had my phone soft bricked (stuck at bootloader) for 15 days till yesterday i managed to fix it. Now i have seen that theres software update available [version
OTA_137.00_152.08] 50.1 mb but i am unable to install the update getting 'error state 7'
I have unrooted the device..
Enabled all disabled apps..
But still error occurs.. Here's the log after failed installation..

正在查找更新包...
I:Update location: /data/media/0/update.zip
正在打开更新包...
I:read key e=3 hash=20
I:1 key(s) loaded from /res/keys
正在验证更新包...
I:comment is 1698 bytes; signature 1680 bytes from end
I:whole-file signature verified against key 0
I:verify_file returned 0
failed to open boot bak sign "/cache/boot_bak.txt": No such file or directory
failed to open boot bak sign "/cache/sbl1_bak.txt": No such file or directory
failed to open boot bak sign "/cache/rpm_bak.txt": No such file or directory
failed to open boot bak sign "/cache/tz_bak.txt": No such file or directory
failed to open boot bak sign "/cache/modem_bak.txt": No such file or directory
failed to open boot bak sign "/cache/aboot_bak.txt": No such file or directory
failed to open boot bak sign "/cache/abootbak_bak.txt": No such file or directory
正在安装更新包...
/system free space was checked.
free space was checked.
mount: Test failed to mount /dev/block/bootdevice/by-name/system at /system: Device or resource busy
Verifying current system...
file "/system/bin/debuggerd" doesn't have any of expected sha1 sums; checking cache
failed to stat "/cache/saved.file": No such file or directory
failed to load cache file
script aborted: "/system/bin/debuggerd" has unexpected contents.
"/system/bin/debuggerd" has unexpected contents.
E:Error in /data/media/0/update.zip
(Status 7)
安装失败
I:Saving locale "en_US"
I:Saving locale "en_US"

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