I've made some search and I see that is an old issue. This happens to me since I joined the game in 2021. Sometimes, when I die to a boss and revive, my character goes invisible then after some time I be disconnected and I get the "eternal error" when I try to login back. I've changed my PC this is still a problem. I remember that happening in a few dungeons like Dephts of Malatar, Moongrave Fane, Unhalowed Grave and I remember that happening a lot inside Maelstrom arena on the Giant boss, Ice arena. Some trials too. I got no clue but to think that's a server issue. Makes it almost unplayable because if it happens in a trial or a dungeon people will get mad at me, and even more because I can't login back for ~10 minutes because looks like the game server put a cooldown and I get errors.