i'm sorry for your loss. i understand what you are saying when you say you thought you would never miss all that annoying tail chasing. we love them in spite of thier problems.My female GSD chased her tail CONSTANTLY. The majority of the advice I got from people who didn't know me was "You're not exercising her enough..she's bored..etc". I took her everywhere to wear her out and had her out constantly. It didn't matter how much I got her out or wore her out physically and mentally, her tail was her arch nemesis that must be caught. She would wake up out of a dead sleep...just to chase her tail.
That being said, I'm not sure about the seizure deal. She ended up passing from bloat/intestinal torsion which I believe was a result of the tail chasing since she had an empty stomach and was inside the house when it happened. I never thought I would miss all that annoying tail chasing