New plug wires are garbage!

Try pulling the wire back out of the boot from the input side, don't try to push it through. Re-crimp the terminal on, and then spray terminal and inside of boot with silicone spray. I use a small, long flat blade screwdriver, if needed, to push on terminal to get it back into boot to proper depth. Then coat inside plug end of boot with plenty of dielectric grease to help from having same problem again.