I've been trying to build a model using C-Frame, and Roblox Studio tends to want to revert it before moving the object. Moving the object with the C-Frame tools is an inconvenience too.
You might be telling it to go to its start position, causing it to revert.
I don't know if I totally grasp your problem, but if I do, try calling
part.CFrame = part.CFrame +-*/ Vector3.new()