It was painted 3-4 years ago. The original builder seems more like a fabricator than a body man. The only reason I touched it was to clean up some welded holes.

I can't see why it would be incompatible. We are both using the same paint topcoat, just different primers. It also waited 3 days before I had a problem. Would the solvent in the 2k primer seep down through the paint and impact the existing primer? I'm not that familiar with the chemistry of these paints/ primers.

I'm not stripping the entire vehicle at this point. That might be a project for a future owner!