Welcome to the ZDoom Forums!

What's your function call look like?

You likely just need the CBAF_NORANDOM flag, otherwise it'll get a random multiplier on top, though it shouldn't end up at 30. The highest should be 18.
https://zdoom.org/wiki/A_CustomBulletAttack

You aren't giving us anything to go on. What kind of crashes, is GZDoom dying or is it a VM abort? Are you using other mods and in what order?

I'd actually considered if it was possible to leverage the feature that exists in UDMF and to a lesser extent Hexen maps of spawn flags by class, but I don't think LevelPostProcessor can change any of those things, and it would not cover items that are spawned or dropped during a map anyway. There ...

The important part. If you were to use consoleplayer in my example what'll happen is each player's copy of the game will spawn different items (if different classes at least) and it WILL desync. Even if you don't care about multiplayer there's no sense in doing it that way, it's potential to break ...

Rough mock-up to show what I'm getting at that you can try in Hexen where Ettins turn into the player's third weapons, but it does miss some important details that again, check RandomSpawner to see what it does for spawning. The biggest ones are specials since Hexen and UDMF can attach actions to ...

First, consoleplayer should not be used to affect the playsim, you need to check the global players array. What about defining your items as normal but have the actual replacement be a custom spawner that uses PostBeginPlay to check the players in-game and which classes exist? Then it can spit out ...

For the SFX spamming issue you'd have to incorporate some kind of cooldown variable. So give your object an int "lasttouched" and then do a test like if(lasttouched < self.GetAge()) play your sound, and then set lasttouched to self.GetAge() + x, where x is how many tics you want the cooldown to last ...

I didn't even see that "minotaurspecial" line before, apparently there's six such enemies but in that case his custom monster may need to inherit from the original one. If all else fails, you can write a custom function like the one the Strife Acolyte or Strife Crusader use. The sure-fire option is ...

The actual special actions for the maps are set in MAPINFO. A_BossDie supposedly just checks if all monsters of the calling type are dead and runs that in that instance so just make sure your replacement monster has it in its Death state somewhere. The actual monster's code, note the first one is ...

Your initial code looks fine but where the return Super.Use(Pickup); you can instead do: bool r = Super.Use(pickup); if(!r) { // Do your print failure message here and maybe a SFX. } return r; The return value of Use indicates if the use of the item succeeded which then gets used by whatever called ...

If the item already rejects being stacked like most artifacts, e.g. Tome of Power, Super.Use should return false, that's the thing you want to check to print your message to the owner. Incidentally the wiki article has void as its return type which is bogus. https://zdoom.org/wiki/Use EDIT: Yep. So ...

The short is that you want to check the doomwiki article on texture alignment since it explains how it all fits together, generally speaking the texture rules work pretty well, but now and again you'll get forced to restructure your map. Maybe less so in UDMF, I haven't checked that out much. As for ...

I think older versions of doom2.wad had an unclosed sector in Courtyard, the one with the cell pack, but even the more recent ones have that door that has two-sided lines on the side walls into void space. Anyway it shouldn't be too hard to determine if a shape is unclosed at least, and you can ...

I'm not clear what the purpose of the script is. The two shapes are one sector, what one does the other does, and you can't break it apart in-game. If you were trying to do something like an area calculation it might be possible to figure out the individual shapes from the sector struct since it ...