Quoting admiralWillyWilber,
And your sure it didn't go through a wormhole.
Enter a wormhole along its' originally plotted path and appear a little farther down along its' originally plotted path, each and every time I've seen this? Yeah... no, no wormholes. Besides, it was not surveying, only exploring by my direction.
Are you playing an insane galaxy.
Nope, Gigantic this time around. It happens on all the top 3-4 sizes of galaxies (the only sizes I play on). As you can see by the other responses, I'm not alone in this experience. The only mods I use are the same custom races I've used since day one of being able to have custom races in the game.