Termite barriers are designed to prevent undetected entry of termites, and, by and large, all the barrier systems out there work. However, when failure occurs it's almost always due to an installation failure. This can be caused in two ways.
1) The installer installs the barrier incorrectly.
2) Barrier is damaged after installation.
The Barrier here has been neglected during the building process, thus allowing it to be damaged.
The barrier here has been damaged and folded over during frame installation.
This pipe penetration appears to have been overlooked during the installation process.
This barrier does not protrude below the doorway & frame. Remedial work would have to be done to correct this.
So always try to ensure that barrier systems are installed correctly initially, and if other trades have to work after the barrier is installed, make sure they understand how it works and what their role is if they must handle it in any way during their particular work on the building site.