It could be your scripts. Is the game lagging itself, or just the Model?
Also, as an experience developer who has been on the platform since 2008, I impart you this wisdom: Don’t use Motor6D. Use Motor instead. It seems Motor6D is riddled with bugs. I use Motor for all my moving joints and I’ve never had one issue. Every time I’m forced to use Motor6D… some kind of headache happens.
The scripts can’t be it because they only lag when they are welded onto something. If they aren’t, they don’t lag and it’s a solid 60 FPS on them.
In this case, I have to use Motor6D because I am more familiar with it and It’s easier for me to script with, than normal Motor.