A "trick" to help with inserting the EC3 connector pins into the shell - -
A Phillips screwdriver that just fits the shell holes for the pins can be used to slightly bevel the shell plastic lock ring.
Insert the screwdriver as you would the pin. It will stop at the locking ring. Give the screwdriver a few turns while pressing
it lightly into the connector shell. Remove, and insert the pin. You should find that the force needed to fully seat the pin is
much less. In addition, the locking ring will have more than enough left to properly lock the pin, unless you went overboard
with the screwdriver.