My partner and I do Borghild fairly regularly. There's an Acid Sigil that frequently gets stuck in the east wall of the first room. It's not attackable, even with AOEs. But it attacks any player regularly, keeping them in combat and depleting armor, making it very annoying. It's also around a couple crystals, which make them unobtainable because the sigil hits you over and over and interrupts you.

We always put in a bug report, and after a few days, it's usually fixed. But then, a day or two later, it's back. We will continue to put in bug reports every time it's back, but it would be awesome if this could be permanently fixed.