My steps:

1) Load ns, open the console.
2) map co_pulse (any co map, haven't tested ns maps)
3) sv_cheats 1
4) givexp 1000 (or any amount, enough to get a welder)
5) developer 1
6) close console.

7) Popup menu -> welder.

As far as I can tell, I can give myself other guns/jps without it happening. Just the welder.

Console is now spammed with "Sprite: no such frame 11" until I change/reload the map. Sort of annoying when testing a map and trying to make sure weldables work. Not sure if it happens in game on a server.

Not sure if this is me only, but I get it every time I follow those steps. It's a vanilla ns3.2b2 install as far as custom sprites/models/etc are concerned.

Not a big deal but I don't see any mention of it in here.