I can't begin to say how many people say their frizzen needs hardening on the forum.
Some are right. Many are wrong.
Have you tested it for hardness?
Have you tried to file it with a medium or fine cut file?
Try filing one of the edges that meets the frizzen face at a slight angle to the face.
If the file removes material, your probably right. The frizzen needs to be properly hardened.
If the file just leaves a bright shiny area without removing any material, the frizzen is fine.
L&R will fix it if it needs fixing.
If you don't have time to use L&R's services and you have a propane torch and some light weight oil like ATF in a bowl, hold the removed frizzen with a pair of pliers above the oil.
Heat the face and upright portion of the frizzen until it is a orange/red color. You don't need to heat the pan cover or the hole this hot so don't worry about that area.
When the upright area and face reaches this color, keep it there for 15-30 seconds and then let it fall into the oil.
Allow it to cool.
After doing this, again test the edge of the frizzen with a flat file.
Again, the file may leave a bright area but it should not cut any metal.
The area where the face of the frizzen meets the pan cover may be soft enough to file. This is fine. You want this area to be softer so it is tougher and less brittle.
For the record, these frizzens are cast out of a hardening alloy steel.
They do not need carburizing or any other special treatment.