Yeah, it seems like it's an issue with item-frames and paintings being entities. A possible fix with be to add the {Invulnerable:1} NBT tag to all of those types of entities in a spawn-protected area. The only problem with this is that even players with Operator Permissions couldn't break them. Servers would have to turn off, disable spawn-protection, edit the map, turn spawn-protection on, and then turn the server back on. This isn't really a major setback, as most servers would edit the world spawn either when the server was offline or in a duplicate file anyway.
Mr. Piggens
Yeah, it seems like it's an issue with item-frames and paintings being entities. A possible fix with be to add the {Invulnerable:1} NBT tag to all of those types of entities in a spawn-protected area. The only problem with this is that even players with Operator Permissions couldn't break them. Servers would have to turn off, disable spawn-protection, edit the map, turn spawn-protection on, and then turn the server back on. This isn't really a major setback, as most servers would edit the world spawn either when the server was offline or in a duplicate file anyway.