Had this happen too, kicks the INS offline and cant figure out how to get working again.
End up with a 'fail' light between the DC and AC standby bus. Which you cant clear, even on the ground unless you reload the plane.
Thank you for finding this. The FO defaults to W/B page and I would normally just close it. But after swapping to another page (route map) and closing it, got 10 FPS back!
Otherwise the plane was a stuttering mess.