What is the origin of the background image layout glitch?

Question

css

On the client's device Safari Browser, resolution 2048x1536 (ipad air 2 iOS 9.0), layout distortion appears - the wrong picture in the background of some elements (adaptive layout on bootstrap3)
Which way to dig?
in the left menu:
?
a bar right above the slider:

and right in the text, where the background should not be:

Answer 1

It would be nice to see a live example. And so - miracles do not happen. If there is such a background, then it is registered somewhere.
First, check the block sizes for different resolutions - col-md-*, col-sm-*, col-xs-*, etc.