I recently upadated to the new patch 5.1, and I unlocked the dungeon The Grand Cosmos. But when I want to launch it, the team forms and then my game crashes, with the following message "Final Fantasy XIV has encountered an error, the program will shut down(.17)".
I tried several times, and it always crashes. Then it crashed a few times on the loading screen when I log in, before I rebooted my PC, which made the game able to load. However the dungeon still crashes.

I have Windows 10, DX11 enabled and working fine. Last year my game crashed in a similar way, I resolved the problem by reinstalling it completely, but now I want to know if there are other solutions because I have a slow internet since a few months.