Help with a mysterious anomoly with fake arms for FPS gun system?

Alright so, I'm getting a tad bit frustrated with this issue I've been having while making fake arms. I've explored many different waystyles of doing so, but I'm not the most advanced coder yet, I'm only a few months into learning. I've gotten the system working for the most part. The thing is, for me to give the system thing such as sway, and walking animations, I need to have an "animation base part" if your will. Basically, you create a part, make it invisible, Weld it to the head and have the fake arms welded to the real arms, then Weld the real arms to the anim base part. That way you have one part moving everything else for the walking and such. My issue is for some strange reason, this method causes the arms to just fall.. I double and triple checked the welds, even got a few good scripters to take a look, no one can figure out what's going on. It happens while in server mode, not studio test mode. Can anyone give me any better methods of doing this? When I get home, I'll be able to paste the code.