I don't know how to run a company, so it's "easy" for me to "give suggestions".
First, there is a clear evidence of cheating (i.e. deviating from advertised specs), on the other hand the failure was not due to this.
Second, the knife is signed by Bura, while he is working with helpers.
This should not be a problem if there is
a.) a reliable system of supervision;
b.) clear documentation of who has done what.
In the absence of that, innocent guys might be accused and the guilty ones might escape consequences. Also, friends, relatives of the accused ones might sabotage later the work the ones who got away (justly or not).
So, I think the punishment in this case has to address the prevention of future problems too, not only to retaliate for the mistake done.
I don't know, what are the customs in Nepal, but paying for the non-spec knife AND for the replacement one seems just and plausible for me.
Additional punishment could be not paying Dasein bonus, or at least not the whole bonus.
At second/further case of dishonesty: the responsible one(s) loose(s) his/their job.
Check lists with every knife: the kami and the apprentices check in front of the manager the actual work performed by them, everyone taking responsibility by this. Helps the payment issues too.
Apprentices can be identified by small marks near the kami's mark (dot patterns?) in case their contribution was important to the integrity of the knife.
The conductivity test as mentioned above, performed by the manager or foreman could help the quality control too.