Sorry, here I don't have the textures, so I'm not sure if I can see any difference between the IPR and render to disk images. In any case, can be the problem related to the takes? You have several ROP nodes in this scene, and if you open the IPR from the shelf icon, the first ROP found is used even to get the render take.
You should try to open the IPR directly from the ROP node that you are using to rendering to disk to see what happens. Can you please attach the IPR and disk images to see what are the differences? Also, what Octane plugin version are you using?
Computer Graphics Software Developer
Octane plugin development and support: LightWave and Houdini