I can't answer your original question because I can't reproduce the situation you describe using the file you provided. I tried exporting as 3D dwg and importing back into an empty model, and all I got was the original 660 Rack component, no other visible text.
I notice that your model contains 16 other unused components containing 3D Text, among them one that contains your mystery "Jimmy Jib Green Case". All but two of them have their edges and faces associated with layer "660 RAck". Liike @DaveR and @Box, I recommend strongly against doing that because it can create confusing issues with visibility. But as you are convinced your workflow is right, I'll drop it at that.
Were you importing into a non-empty model? I suppose it is possible that this layer usage could be interacting with something if you import into a model with other prior contents and layers.