If it's that old it could use several upgrades...and when I've sent locks in that old, they've just sent me an entire new production lock assemblies.
Please take this advice: Put together a nice memo with the lock and priority mail it directly to the attention of TC's Service Manager Tim Pancurak.
DO NOT call ahead of time, and under no circumstances discuss it with the rank & file in the customer service center or repair department...some of their attitudes are like they're paying for it out of their own pockets.
Mention that you like the TC Hawken but the lock is simply not reliable...can he look it over and get it to the condition where you can trust it, can count on it for accurate target shooting and deer hunting, etc...you get my drift...he'll take care of you.
Send it Priority Mail / Delivery Confirmation:
Mr. Tim Pancurak
TC Service Manager
PO Box 5002
Rochester, NH 03866
As busy as they are right now, he'll probably just tell someone to pull a new lock off the shelf and send it right back out to you...I think he's replaced 3-4 complete locks for me...several others on the board have followed this approach with excellent results.
The redesigned TC locks are really flawless now...work great with Tom Fuller 3/4" wide (x 7/8" long) BEF's...and get yourself the redesigned vent liner if you don't already have it...and I wouldn't stay with the TC equipment if they weren't 100% reliable...deer hunting is too important to me...I've now filled 16 buck and 6 doe tags with them and they've fired like a .30-30 every time I've dropped the hammer.