If you have bootstrap framework in the 3rd party libraries in your project then you probably do not want to touch the original sources but overwrite them. Here is how to do by compiling the less files.
Always stick to theses essentials:
Understand the problem before you fix it .
Check for common defects.
Refine the test cases that produce the error.
Narrow the suspicious region of the code. / Expand the suspicious region of the code.
Be suspicious of classes and routines that have had defects before.
Check code that’s changed recently.
Set a maximum time for quick and dirty debugging => rewrite the code .
Change the code only for good reason AND Make one change at a time.
Never debug standing up :)