So I recently posted a bug about the Sniper and the Concheror. If a Sniper blows the Concheror, the server will crash. GrampaSwood undid the edit asking me for a source. Unfortunately, I cannot provide one since I was not recording when it happened and it is very hard to replicate. Also, I have not found any videos online. I'm pretty sure that a seperate plugin can be used to give a class any item, so try that and if it's true, post it.
Topic on Talk:Randomizer
This is a known issue with certain sequences/pose parameters on the Sniper model/other models when a class gets a weapon that it isn't expecting to have. There's a catch-all fix at AlliedMods by User:Benoist3012. The thread's titled "[TF2] Thermal Thruster Crash Fix".
The crash occurs for several different combinations of items/classes and may only occur for certain animations (e.g. the Inspect animation), so it may not be useful to specify just the Sniper/Conch interaction. Not sure what the right note to put here is, but it should definitely be more general than just those two.
