Door lock replacement

A home owner from virginia says:
My current lock is from 'The Atrium Lock'- which is 28 years old. It broke.
Need a replacement to match the exact holes on the door. Picture with parts with a scale in it should help with the size of the lock.
Please let me know if you can help
Atrium lock
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Dave Sr. from SWISCO responded:
Thanks for your interest in SWISCO.com. Please take a look at our 82-400 handle set. This could be the Atrium lock set you are looking for.
A home owner from virginia says:
Received the part.
Installed well. See photo.
But the inside handle does not stay, even when the set screw is installed all the way.
In does not get tightened, but falls into the cavity.
See attached pictures.
Need to resolve this.
What should I do.
Atrium door handle
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Dave Sr. from SWISCO responded:
Take a close look at the spindle that comes with the new handle. The spindle has a notch at each end for the set screw to tighten on to. Make sure you are installing the handle set screw in the notch at each end of the spindle.
A quick learner says:
I know how to install it properly.
Set screws are both in the notched grove.
But it does not sty tight.
It comes loose after couple of times of use.

What can I do?
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Dave Sr. from SWISCO responded:
What I've done in this situation was to put a few drops of a liquid lock washer on the screw threads. This acts as a type of adhesive to keep the screw tight, but can still be removed it you need to take out the set screw in the near future. You should be able to find this at a local hardware store.
A quick learner says:
Thanks
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