Switching between header and source (via F4) doesn't always find the correct file. It only finds the first matching filename.

If you have two identically named files, (but, for example, located in different folders), F4 will only ever return the first file.

E.g.:
include/libraryA/Widget.H
src/libraryA/Widget.C
include/libraryB/Widget.H
src/libraryB/Widget.C

If you hit F4 on Widget.C, it finds libraryA/Widget.H instead of libraryB/Widget.H.