Game Mechanics: Strange invisible player bug?

[Nulek]

The other day in Unrest a player was invisible to me without see invis, but had an active pet. When I cast see invis I could see they were casting spells and other actions without invis breaking.

Yesterday in The Feerrott, a ranger invis'd me to zone into Oggok to rez him. When I zoned in and rezzed him he could not see me. I wonder if it is the same bug.