Help! Problem laying bed wood

[AusTx68]

This afternoon I started laying my newly varnished wood and ran into a problem. Not sure why this is happening and figured someone may have seen this before. The two pieces of wood that have the bolt holes will not lay flush because of the frame rivets shown in the photo. There is a very small space between the wood and the frame cross member. Maybe 1/8". The head of the rivet is taking up that space so the board will not lay flat. I imagine I could put spacers between the frame and sills to raise the bed but I didn't think this was necessary. Has anyone seen this problem??