engine error

I'm trying to test my new map on sv_pure 2 but I get an engine error and the game crashes.
I've created LDR cubemaps with this tutorial: https://tf2maps.net/threads/tutorial-cubemaps-and-how-to-make-them.25699/
I've also packed everything with VIDE (there is no nav file (which usually cause crashes))

Is there something I've missed causing the crash? pls help

 

What is the engine error you are getting

 

It says: failed to lock vertex buffer in CMeshDX8::LockVertexBuffer: nVertexCount=2204, nFirstVertex=0

 

So I've tried deleting the bsp file and starting over again but I still get this error
https://i.imgur.com/oB8GsMa.jpg
I still don't know what causes this