When you remove the ground from a blockland map (like my spacebuild mod does) save the bricks, shut down the server and reload them, they have no ownership.
I've been trying to think of ways to fix this. In spacebuild, the floating brick restriction is removed so players can build anywhere and hammer any brick they want. Also removed is /undobrick and /clearfloatingbricks for this reason. It works perfectly.
One method I thought of was to set isBaseplate = true; on every planted brick. Would this cause them to save with ownership?