key lock install question

Hello,

I have recently followed instructions and installed the #82-310 key lock in my existing estimated 5yr old handle & mortise lock. It completely fits in my handle & mortise lock, no problems there.

However, this new key lock seems to need to make a full turn to lock and/or unlock. But my mortise lock seems to only need a half turn to lock and/or unlock.

I am sure the tailpiece is at size.

Can you advise?

Thank you,
Ted & Kathy