So basically I have this unexpected error where it says
Left Arm is not a valid member of Model
I shouldn't have this error because I'm using r6 and I checked it it says Left Arm so I don't understand. I have the whole script if you need it comment but I find it reasonably not to post the whole script for this will waste space. My script...
LeftH = ctr["Left Arm"]
Sometimes there is latency when instances are streamed to the client. I'm assuming you're getting the character from CharacterAdded, which will fire before the character's model is populated with limb parts and other required instances.
If you're sure that an instance bearing this name will eventually exist as a child, you can use the WaitForChild() method inherited by all instances.
LeftH = ctr:WaitForChild("Left Arm")
This will yield the current scope, so you should only use this method when you're absolutely certain that the child will exist at some point in time.