re: seems to occur frequently in this location
The recurrence, and the slow travel speed suggest that it is a natural atmospheric phenomenon. Some sort of high-altitude cloud, perhaps?
"Noctilucent Clouds" are visible many hours after sunset or before sunrise due to complex refraction paths around the arth's layered atmosphere.
Alternatively, it may be re-entry debris from a recurring series of space launches, or just chance meteor trails.
Wait long enough and strange events accumulate SOMEWHERE. That's how statistics works...