one of my parts which had a potential of excellent has now changed to very good after I started work on a new design based from it! - is this meant to happen?
I think James is right. I have to Chassis, both came out with exactly the same ratings yet one has already seen a level drop. This suggests that the one that dropped was right on the threshold when designed.
I think what you are describing Daniel is supposed to happen. If you have researched a part to Excellent, then start designing a part, you will see the research level drop one to very good. Happens for all parts.
The annoying thing is if your designer builds a dud part, you are no longer at the desired research level to re-design that part.
The researched level is what the part is being based on. e.g if you start a part at excellent then that part will be made to a research level of excellent. When you start a new design the research level drops but from what i understand does not effect the part you started to design