I have just seen this, and i have never seen it before. People did spawn from it, and they went to the station to change class, but 4 C4's and no damage at all, no smoke.
Ok... did that wizzard sundi maybe...just maybe... a kind of wizzard shield bubble (Quite tight, not like the cloaking one)? Does it get shiny and sparkles if you shoot it with a handgun? Bad news: This is a deploy shield sunderer! It generates a shield that can take up to two tankmines or C4, before the sundis HP can recive damage. Oh: that shield also regenerates. Just FYI.
I know that such a bug existed a long time ago. There was the possibility of a sunderer becoming immune to all damage when deployed. But it was rare.
Yes, long time ago and it was fixed. Was in the time with invincible players also happening (warpgate protecion was out of hand).
