Catalyst damage

I removed the catalyst in our Buck 80 a few weeks ago to clean it and noticed quite a bit of damage on both the upstream and downstream faces. It appears to be similar to photos of flame impingement damage, but it doesn't make sense that the outlet would have the same kind of damage, since it isn't exposed to the firebox. In fact, it seems to have more damage.

The flame shield and wire grid have always been in place and I don't burn super hot. This is after four seasons of use. Any suggestions as to the cause? Thanks.

Thanks for all the replies. I'll try to answer all the suggestions below. Btw, the cat is a Firecat from Applied Ceramics. Any opinions about them or good things to say about another mfg? There is apparently no 6"x7"x2" steel cat available.

The door gasket is fine and I've not had trouble getting the stove to run w/o visible flame.
I cleaned it using the distilled water and vinegar method. Plan to buy a replacement to have on hand if it doesn't work well.
Wood is well seasoned (2+ years) and stack tops are covered.
It's possible I've reloaded with a too hot cat or reengaged bypass too quickly.
Cat probe is same age as cat and pretty degraded. Will order new one with new cat.
The cat is not cracked, just the faces are crumbling.

The flame shield was a bit distorted when I removed it to remove the cat. I flattened it out and tack welded on a few stiffeners to hopefully keep it flat. There were two small stiffeners right under the cat, but none toward the back of the stove. Perhaps that distortion was allowing too much flame to get up to the cat. There is also a wire grid that is suspended in the cat housing that is supposed to do something to any flames that reach that point.