I recently purchased a lightly used Canon 6D on eBay as my first real astrophotography DSLR (I am very much a beginner...). This camera, when I received it today, had less than 8,000 shutter actuations, and had no signs of wear or damage. The first thing I did when getting the camera was to test it for defects and issues, and it seemed to pass my initial (newbie) inspection.
It was not until tonight while attempting to image a nebula that I noticed the images I was capturing had tons of white, blue, and red speckles covering the image (which clearly was not normal noise). This obviously scared me, and I did much research to find out that the camera sensor has many stuck/hot pixels. I attempted many fixes, such as the popular manual clean sensor method; however, attempt after attempt left me with the same result. It seems that it is often the same pixels causing the issue, and this makes me think that the sensor may have more than just stuck/hot pixels.
I know that a few of these pixels may be unavoidable and can be fixed in post processing (with dark frames, etc.), but this many affected pixels seems to me to be a very serious issue, and I am out of ideas to solve the problem without spending more money (on what was supposed to be an affordable camera...). Does anyone know what may be wrong with my camera sensor and if there is a way I can fix it?
Thank you all so much in advance for your help!
P.S. Below is an attached image of a 30 second dark frame at ISO 1600. I'm not sure if the pixels will show up for others, but the file on my computer shows an obvious and large number of these pixels, even without zooming in....