Are you using a proper tool to squash down the connector pins onto the wire? And are you definitely wiring them up correctly. You should be able to visually see the connector pins punched down and through the wires. When I make mine, I have to clamp the tool very firmly to ensure all wires are clamped properly.
A simple way to test the wires yourself with a multimeter would be to strip the tips off each colour pair and twist that pair together at one end. Then all you would have to do is check the continuity between the colour pair at the other end. It would check the full length of a colour pair in one go.