When I was taking pictures of M99 Galaxy using my Seestar S50 in Alt Az mode, I had gotten roughly 1,600 frames over the course of 3 clear nights. I was getting almost perfect frame acceptance rates, as I was only doing 5 second exposures from my Bortle 8 location. When I went to use Deep Sky Stack for all these accepted frames, it only used about 600 frames. I selected all the frames, and it rejected so much time spent gathering data. I went through to try and keep as many frames as possible where the rotation did not fully interfere with the stacking process. I'm just curious what I could be doing wrong because this is the only time it's happened to me where I've had so many rejected frames.