Random black screen, forces me to restart due to massive lag afterwards

Every now and then, my screen goes completely black for a few seconds while playing FFXIV. Now, in itself this isn't that much of an issue, but after the black screen my framerate will drop to around 1/3 of what I normally have, making the game pretty much unplayable. I have not found a way to get it back to normal without restarting my game.

The black effect could happen after as little as 5 minutes, and the longest I've played without having to restart is about 2 hours. Needless to say, this is ruining my game experience. Before the black screen glitch effect triggers, I play on maximum settings with a solid and stable framerate on pc. I've tried reducing the graphic settings to minimum after the black screen occurs, but with absolutely no change in framerate. I have a beast of a computer and don't have this issue with any other game, and my screencard drivers are updated. I simply have no idea what's causing this or how to fix this, any help is appreciated. I tried reporting this through in-game customer support yesterday, but still no answer.