There are still some things you can test to see what the problem is.
How is *your* battery when there is no bootloader installed?
First do a good test repeating a video while you have the bootloader installed and time it.
Then try doing a restore, then playing the same video until the battery is dead, and timing it.
Now when you compare those times you will have a good test of the effect of the bootloader on battery life.
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