Sometimes, you will have a fuel leak from an injektor return line that will run down the side and give the appearance of a leaking pre-chamber.

In other cases, I have seen a pre-chamber come loose (because you can't tighten them to 100 lbs/ft by hitting them with a chisel) and the resulting soot buildup will allow compression to escape past the chambers.

A thorough cleaning of the chambers and the sockets in the heads will be required...Bert