I live in Australia and during my recent trip to India, I bought an Android One phone called the Lava Pixel v1. The phone is running Android 5.1 and since I have gotten back to Australia, the phone notifies me that I have an update that I need to install. It downloads the 770 mb update and when I try to install it, it shuts down and restarts the phone and then starts installing the update, I can see the Android mascot. After it(the install progress bar) gets to about 20% or so, I just get a message saying "Error" that is all. The Android mascot is lying down or so and from it's open belly there is an exclamation icon (!have a look at the attached image for what it looks like). At this stage there is no sim card on the phone. Additionally, some apps like Facebook fail to install. Facebook messenger can be installed. I am a developer and I have purchased this phone mostly for dev purposes and would like to get the latest update for my new Android phone, so would appreciate some help with this.
The apps failing to install and the system update failing to install are probably unrelated.
For the most part, the system update is just a big zip file that gets unzipped to a protected part of the storage. You can't write to the protected part while Android is running. Unfortunately there are a range of things that can go wrong here, and during the system update the bootloader doesn't have a lot of code. (We're talking bytes, not megabytes.) Any descriptive error message it would give would be useless to a user anyway, as you can neither fix the bootloader nor fix the 770 mb update.
I would recommend you contact the manufacturer (or whoever is pushing you the 770 mb update).