The render plinth was originally applied to try and keep the damp out. It usually has the opposite effect and traps moisture. Someone then had the bright idea to hack off the lower section to allow the bricks to breath - so far so good; but then went ahead and injected a chemical DPC which was totally unnecessary.
This is what happens to soft bricks when a sand and cement render plinth has been applied. The trapped moisture tries to escape through the brickwork and through frost action causes the face of the bricks to spall. The injected DPC was unnecessary.