Full disclosure: I am still really new at all this, having just started in the last few months.
Before painting smaller pieces such as suspension and engine parts, I always do fitment tests and file or sand as needed to ensure a good fit. After painting, I occasionally experience fitment issues during final assembly, and I think the root cause is I might be overdoing it with the paint.
I primarily use lacquer-based primer and paint, and occassionally acrylics for hand-brushing. I almost always use 3 light primer coats, then 2-3 color coats. I never clear coat smaller parts.
Anyway... Does it sound like I may be using too many coats, or maybe laying them on too thick? I am not sure why I'm even using three primer coats on these parts. My inner voice is telling me if the part is adequately covered after one to two coats of primer, or paint for that matter, what good are the additional coats doing?