[Al Skierkiewicz]

FTC,
The connector pairs should mate with significant friction to hold them together, provided you do not have tension on the wires that will pull them apart. It is possible that you have bent contacts (as shown in the Powerwerx link above.) If the contacts are bent, (or are not free to move within the housing), the contacts will not mate properly. This occurs for two significant reasons. The first is using an improper crimper. This causes the terminal to be bent and will result in a lot of force needed during contact insertion. The second results from soldering the terminal which may result in excess solder causing the same type of misalignment as with improper crimping. While many crimpers will state they can crimp these contacts, only those specifically designed for APP contacts actually do the job.