Weapon model with armature are imported as separate object and have bones copy pose constraints added that are targetting to playermodel bones

ERROR: [Errno 2] No such file or directory: 'C:\\Users\\throw\\OneDrive\\Documents\\blender\\models\\vtuber\\f_c_body_LOD0.smd.dmx'

It literally tells...

https://github.com/REDxEYE/SourceIO

It's SourceIO, not source tools. You should redirect it to SourceIO author instead

Link is broken

When it happens?

Put definebones lines

Refer to license agreement of game you took model from

Yes

Początkowo opublikowane przez Tiny Desk Engineer:

Początkowo opublikowane przez xdshot:

Static props don't have animations, even if it's mandatory to have at least one

It's a physics prop, not a static prop. I already knew static props don't need sequences, I literally mentioned it in this discussion.

Początkowo opublikowane przez Tiny Desk Engineer:

because apparently every model requires at least one sequence unless it's a static prop

Same for physics props.
Export mesh, apply it as sequence as well