I get similar problems with my C11, and the longer the subs are, the worse the distortions get. The reason in my case is that the exposures are way too long for the bright stars. The brightest stars are saturated in a few seconds, and the rest of the exposure is integrating the halo that you don't even want to see. Any internal reflecting surface in your imaging train can cause spikes, offset halos, etc.
One solution is to avoid positioning bright stars near a corner or edge, if possible. Another option is to take a separate set of exposures of very short duration, and use them to replace the "burned out" stars. However, perhaps the best solution is to shoot some narrowband frames and use them as the luminance channel for your stars. I'm assuming you're using an OSC camera with your RASA, but there are narrowband filters that can be put in front of the camera to shoot a grayscale image. With my C11, the stars are so much smaller with narrowband filters that it's quite shocking.
