My dev levels have gone up now after dropping.
They dropped a level or two after I produced that part, but three days later they are back up where they were.
I designed a fuel tank over a week ago. Dropped to unsure, now it's up to very good. Haven't used a single staff member to jump it up, just left it blank.
My designer is superb/superb and I've ignored everything about the new system and played the old way.
New parts are coming out as unsure research level and good at production.