Broken Breedfiles
I booted up Petz 5 after one of my long hiatuses and realized a lot of my old breedfiles had gotten... weird. Or maybe it was a problem I was ignoring before. Certain breedfiles wouldn't breed. Looking on Petzcord, I found out there were other people with the same problem. So, I took it upon myself to start fixing them. If you are the owner of one of these breeds, please reach out to Catz on Petzcord, and I will properly credit you if I can't find the credit or if you would like to discuss the terms of me hosting your fixed files. I will try to include instructions for how I arrived at each fix, but I have come up with a pretty standard formula.
If a breedfile is unbreedable, I copy all the information in each section that shows in LNZPro into a fresh base file. I.e. if there was a non-overwriting breed based on an Alley Cat, I'll pull up an Alley Cat and start pasting in the info, ignoring any sections in LNZPro that seem glitched, as I've seen in a couple cases.
However, sometimes there is a part of the code that isn't working properly. I've noticed in a few of Carolyn's breedfiles, there is a section in the String list that's missing that needs to be there in order for the file to be able to breed. This missing bit is usually found in LNZPro under String list in a loaded file, then section 63 under index 1002.

If the highlighted part reads <empty> instead, it must be filled with the breed abbreviation. The breed abbreviation should be found in the same spot in the base file.
Other times, there is a more complicated problem afoot.
Without further ado, here are the breeds I have fixed so far. If for some reason they are broken for you (i.e. unbreedable) consider repeating the steps outlined above, or send it my way and we can figure it out together.
Paranoia's Aliumz (Petz 5 only)
Paranoia's Aliumz was the one that started it all. I thought these were just the coolest, but I was confused when my game started crashing every time I got one of my Aliumz to mate with one of my other petz. At first, I thought my other pet, a Trinket cat, was at fault, but eventually I came to see Aliumz was the problem. Aliumz I didn't have to do anything extra for. This was the one I patented my copy-to-fresh method for.
Carolyn's Pastel Ecunny (Petz 5 only) Carolyn's Charcoal Angora (Petz 5 only)
With the success of one file, I next turned my gaze to a few of my files that had loaded in with corrupted names and of course, would not breed either. For these I did not need to employ the copy-to-fresh method. These only needed the missing breed callsign in the 1002 index as described above.
Sassy Tabby.cat (Petz 5 only)
This file was extremely corrupted. It had lots of little bits and bots in its LNZ file that were not needed. Copy to fresh worked for this one.
Cheshire Cat.cat (Petz 5 only)
This one would not load correctly into PetWorkshop. It would crash it immediately upon load. Through the process of elimination, I discovered that there were some addballz needed for the file to load that had been deleted. This file was fixed by using a fresh Tabby and omitting/deleting the addballz in PetWorkshop rather than LNZPro. It is a rather simple omit-everything-except-the-face edit, so it was easy to just retrace whoever made this's process. (if you know who made this, reach out to me on Petzcord (Catz)!
WIP: Bobcat VPZ
This file I got from Vickie's Petting Zoo on archive.org, but the LNZPro output looks very bad. Lots of stuff that doesn't seem to serve any purpose, entire random sections of empty bytes and corrupted text. However, so far it looks like what's actually throwing the error is the textures. I'm still experimenting to see what change to a default Alley Cat will crash the game. Stay tuned while I fix Vickie's Bobcat!