As any mechanic will tell you, an E-brake that won't quite hold usually means that you need new e-brake brake shoes. On the VX and others, they live inside a drum that is built into the rear brake rotor. Not too difficult to replace and well worth the effort.

DO NOT adjust the cable to try to get them to work!! This may seem like a quick fix, but in reality the shoes are nearing their mechanical limit and still won't reliably hold the vehicle on a hill. Adjusting the cable only means you'll have to re-adjust it again once you finally replace the shoes.