There's a quest that reveals the system the unique planet Sykagoja is located in. I think if this unique planet hasn't spawned naturally the quest will spawn it in somewhat near you. The problem is once the system is spawned in it's impossible to travel to, it gives the error "No valid visible path: Explore the galaxy more, or research the technology Autonomous Materials," even when Autonomous Materials and Baryonic Shielding (free travel) are already researched.

Here's a save with the issue, if you need it. The Sykagoja planet is in the Deki system, I have an exploration fleet with 25 movement and x3 free travel speed that is unable to path to it.

UE 002.zip

I wanted to post this bug, but Astasia did it already, so hereby I confirm this bug, same situation.

I've also had this quest when I already know where Sykagoja is!

I don't know if this bug is already known by the devs since there's no reply, but I've got the same problem. I couldn't visit the planet in two consecutive playthroughs. I hope this gets fixed someday. :)