I haven't gone back to see if this is a recent issue or not, but it seems that as of Octane 219.1.5 and C4D R21, the Octane Cubic Panorama Camera has the positive and negative Z axis reversed from what C4D itself uses. I know different programs use different directions for +/- Z, but since this is in the C4D environment, it really should agree with the host app.
In this example, the rendering Octane Cubic Panorama Camera is placed at 0,0,0 with rotation of 0,0,0. Here are two top views and the resulting renders from + and - Z.
It also seems to be rendering mirror images of each of those POVs.
Unless it's just been too long since I used cubic maps, and this is the way it's actually supposed to be, - but these definitely do not represent the camera's POV along each axis.