Adjusting spring fire door hinges?

The door from my kitchen to the garage is a fire door, fitted with 3 self-closing Arrone spring hinges. (either AR8280, AR8281, AR8282), in place of the traditional overhead door closer.

When fitted by the chippie the door closed beautifully - closed gently, with a soft click on shutting, but the plastic seals & brushes were not put into the frame at the time. Afterwards, the builder put the seal strips into the frame - with the result that the door wouldn't close unless slammed shut. He refused to do anything about it, saying it would "bed in" over time. That hasn't happened. I have now taken out the bushes that were in the plastic seal strip, so the door now closes again, but it closes with a terrific slam. Seems the spring action in the hinges has gone awry (not surprising really). I have the leaflet showing how to adjust tension during the fitting stage, & the allen key to do the adjustment. There is a tension locking pin that holds tension in place.

To do the readjustment I need to remove the tension pin but unfortunately, there doesn't seem to be any way to remove it once it has been pushed in fully. Does anyone know how to remove the tension pin safely, without damaging the hinges?