Hey everyone, I would like to provide a little update on this seemingly abnormal blooming on the KAF8300 sensor. First, I would like to thank you all for your comments because you have helped me narrow down the issue and very likely to the solution to it.
Yes, the mechanical shutter was getting stuck, so I decided to remove it and while doing so, I realized that there was a little metallic pin on my SBIG ST8300 that serves as a rail for the shutter. This pin was putting some friction on the shutter, so I decided to check what was going on the opposite side of the electronic board where the motor serving the shutter was located. When pulling off the shutter, that nice little Japanese motor was working as expected, so the friction was probably causing it not to freely move around or perhaps the motor was not getting enough amps to actually do its job. Then I checked the two allen bolts arrowed on the picture below, and confirmed they were loose, so the former problem was the most likely issue. So, I gently moved the fan towards the top of the image while giving the required torque to the bolts, which in turn allowed the pin (located on the opposite side of the electronic board) to reduce the friction on the shutter. Voilà! The shutter was now free to move around and the motor was activating and closing the shutter as expected. So, before the moon and the clouds arrived late during the night, I decided to repeat the session on IC2944 (I am located in the southern hemisphere in Chile, so this object is near the zenith at the beginning of the austral autumn night). Needless to say, the blooming effect was gone and you can see what the image now looks like after some minor postprocessing.
In conclusion, the KAF8300 does require the shutter to avoid readout trails from bright objects while reading on a row to row process. Secondly, sometimes there are easy to solve mechanical problems. In this case, you would want to make sure the shutter is free to move before going for an expensive motor replacement, so a bolt torque check on the cooling fan should be required from time to time. Hopefully, things should go back to normal now. I mean for the camera, not for us out there in quarantine.