Unable to upgrade OTA Marshmellow update on HTC Desire 826 Dual SIM

Hi All,

I have recently received OTA Marshmellow update for my HTC Desire 826 Dual SIM. I have not rooted my phone. But while installing the update, recovery screen appears with below error msgs. I tried after factory reset but didn't work. Can anyone help me to understand what this means ? and how it can be solved ?

E:missing bitmap oem_unlock_bg
(Code - 1)
E:missing bitmap oem_unlock_bg_yes
(Code - 1)
E:missing bitmap oem_unlock_bg_no
(code - 1)
E:Find no match PARTITION: for package path @/cache/recover/block.map
Finding update package...
Opening update package...
Verifying update package...
Installing update...
L50QCT. 01 . 103 . 015
Verifying current system...
system partition has unexpected contents
E:Error in @/cache/recovery/block.map
(Status 7)

Installation aborted.

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