I'm getting this onto my console with some add-on
[ARC9 Weapon Base] lua/weapons/arc9_base/cl_model.lua:40: bad argument #1 to 'LookupSequence' (string expected, got nil)
1. LookupSequence - [C]:-1
2. GetAttachmentPos - lua/weapons/arc9_base/cl_model.lua:40
3. GenerateAutoSight - lua/weapons/arc9_base/cl_sight_autosolve.lua:2
4. BuildMultiSight - lua/weapons/arc9_base/sh_sights.lua:127
5. PostModify - lua/weapons/arc9_base/sh_attach.lua:125
6. ClientInitialize - lua/weapons/arc9_base/sh_init.lua:108
7. unknown - lua/weapons/arc9_base/sh_init.lua:33

The one I was using is arc9_fas_sr25 to spawn in and this appeared on my error console. I did type this Arc9_reloadatts and it seem to fix it.