"UFO" captured during continuous long exposures

Today I took over 400 long exposures of the night sky. A few pretty large meteors, which were out of frame, and early on in the night I saw something really extraordinary; this one in particular I didn’t get a full recording as it literally disappeared into the night sky. I was very close, as in a second, from capturing a meteor which I only saw on my camera display, and it appeared to make the display very bright! Unfortunately, the camera was delayed by the time I took a photo. I did, however, capture something interesting after I set my camera, which was connected to a remote shutter release to take one photo immediately after another, on a tripod. I used an ISO of 12800, and shutter speeds were two and a half seconds. Aperture was f/1.8. The object moved through the frame for a total of 117.5 seconds, or nearly two minutes, as the camera was set to 28mm focal length. I merged 17 of the photos together to try and show what a single, 42.5 second exposure would have produced; as you are able to see in the following photo, the object faded out against a cloudless sky for about five photos, or about 12 seconds. There was an interval between every photo, which is why the streak of light isn’t a single continuous line. I don’t know what it is, but maybe someone has a clue. I’ll have to check the satellite database and time of capture of the photos. I can also calculate the magnitude, to see if it matches that of any satellites that could match. Honestly, I’ve never seen this phenomenon before except for that video that I recently posted onto Youtube. There are advantages and drawbacks to when you decide on a compromise whether shutter speed, or ISO. A longer shutter speed would make the object appear nicer, but if that coincided with the high ISO value, then the amount of noise would be very high. And going too low in terms of an ISO value would make the object very dim, as 12800 is very high. I suspect that the object was extremely dim, so I’m not sure if it could’ve been a reflection of the sun. Edit; I don't think you can see it here, but one of the frames which might not have been included, shows the object got brighter towards the end of the frame. It might have been a plane, but it's difficult for me to conclude whether the object was or wasn't blinking, even though I mentioned previously that it was because of a delay between photos. Each photo is essentially the same as a frame grab from a video, except of course, the shutter speed was 2.5 seconds. I can verify that there was a delay between photos, as the camera did process each photo, which took time, and if the object were blinking, my guess is that the lines wouldn't all be of the same length. Then again, this is very difficult to determine.