Hi Terry,
If the streak is in all the subs then it won't reject because in each sub all the pixels that define the streak are bright and therefore no matter how many pixels are identified as outliers by the rejection algorithm, the remaining pixels are bright and the streak persists. This, of course, is different than an airplane trail, for example, where the bright pixel that defines the trail is in only one frame and is easily identified as an outlier and rejected.
I have seen similar steaks that have turned out to be do to a bright star just outside the field of view and positioned such that it caused a reflection. For me it happens very rarely and is a fluke of positioning that somehow presents bright enough light at a place where a reflection can occur. The star doesn't have to be extremely bright. I have had this with an eight mag star that was in the one position for my image train where a reflection was possible. You can look in your planetarium program with your camera icon in place and see if there is a bright star adjacent to the field in line with the reflection. You can then get rid of the streak by rotating the camera and using a different guide star. If the streak is gone with repositioning then clearly a bright adjacent star was the problem.
Steve
