How to tween Model:SetPrimaryPartCFrame()

[g_captain]

Adding to OP’s reply and quoting from the linked thread:

@lesserfantasy

A way to fix this issue is to handle SetPrimaryPartCFrame yourself with a custom full-Lua implementation. In this implementation, you cache the CFrames of every part except the root in a dictionary and manually offset them from the PrimaryPart when it moves. This is done by multiplying the inverse of all the part CFrames by the PrimaryPart’s CFrame. This keeps all model parts in relative space to the PrimaryPart.

local offset = primaryPart.CFrame:ToObjectSpace(boundPart)
primaryPart.CFrame = primaryPart.CFrame * CFrame.new(1, 2, 3)
boundPart.CFrame = primaryPart.CFrame:ToWorldSpace(offset)

-- You can also use CFrame inverse, which is what ToObjectSpace is internally

primaryPart.CFrame = primaryPart.CFrame * CFrame.new(1, 2, 3)
boundPart.CFrame = primaryPart.CFrame:Inverse() * boundPart.CFrame

If you strictly want all the parts to be anchored, this is a method you can probably bind to a CFrameValue tween and property change. But this is a complicated workaround.

As the post describes and previous replies, it’s the far easier choice to tween one anchored root and all the other parts welded to it.