It is good practice to prefix the includes from one's C libraries with a directory so that they are all part of the same 'include namespace'. Unfortunately the Nordic SDK doesn't do this, which causes problems if another library is being used with header files with the same name. Why does the Nordic SDK not follow this good practice?
For example, this include:
#include <app_timer.h>
should be something like:
#include <nrf/app_timer.h>
Examples of libraries that do this well: glib and GTK.