If you’re using Bootstrap for projects, including but not exclusive to WordPress, you may come across issues such as pages not responding correctly on devices such as iPad mini.
In my instance I couldn’t get the navbar to collapse correctly in either landscape or portrait mode. Nothing I tried worked for my “twentyseventeen” based themed project, despite the fact that all other settings I worked with did obey my directives.
I found the solution was to modify the bootstrap file using LESS to apply settings such as “@grid-float-breakpoint”.
Rather than going into a lot of depth regarding LESS and compiling a compiler to set it up, I went to the Bootstrap official website and used their online compiler which generates the customised version of bootstrap.css & bootstrap.min.css
From here you can apply your modificatios and allow it to generate the new file which you download and transfer to your website.
https://getbootstrap.com/docs/3.3/customize/