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Spark plug wires

number 4 spark plug wire comes off the spark plug after i go a few miles. it feels like it is clicking into place but still comes off. I crimped the clip in the wire thinking it might be a little loose. Brand new plugs and wires

Are these replacement wires? Do they have enough stress relief (enough looseness to accomodate movement without pulling the wire)?

If the wires are original, perhaps it’s time for new wires. Perhaps the clip has lost its spring tension.

Is the #4 plug fully seated? (no combustion gases leaking past it to blow the boot off)
Engine and year?

Might you have put a short wire where a longer one needs to go? Any of the others seem to have extra length?

It’s hard to get to but I feel like it’s in good. I switch the # 1 plug with the #4 to see if it was the plug but same problem. 99’ expedition 4.6.