Ignition coil tightening

Followed your video to change the spark plugs on my car (it was extremely helpful). All was good until I attempted to reinstall the ignition coil using the 10 mm bolt that screws into the engine block(?) For the far right (as you face the front of the car) spark plug. The bolt would not tighten down. The first 3 tightened down as expected, while the last one would tighten down and then loosen as I turned the bolt clockwise. I tried exchanging bolts between positions 2 and 4 (last one) and it was not the bolt but rather where the bolt threaded into.

The ignition coil for position 4 (far right as you face the car) is held loosely into position by the bolt while the other 3 ignition coils are held snugly into the place.

Is there any action that I can take to secure the fourth ignition coil into place? What problems should I expect if no action is taken?

Thanx for your reply in advance.