It's unlikely the plugin has caused the issue. At some point I would guess that you have loaded the file pz3, loaded into in the Octane plugin, changed the octane carpet node, and then saved the pz3 file. Or conversely, loaded the scene into Octane without a rug texturemap in the Poser material, and then applied the rug texturemaps to the Poser material after the rug material had already been converted to Octane.
Once you have converted a Poser material to an Octane material for a scene, if you change the Poser material, the Octane material does not automatically get updated (because the plugin doesn't know the Poser material changed). So when you change a Poser material, make sure you reconvert that material in the Octane plugin if you want to pick up the new Poser texturemaps. Or even better, don't change the Poser materials, just edit all your materials in Octane.
Hope that helps.