An unexpected error has occurred - KERNEL32.DLL

I always get this message below when delivering the final blow to the boss in the quest "Death Unto Dawn" from 5.55 patch.

An unexpected error has occurred. Exiting FINAL FANTASY XIV.
2021-11-27_15:17

ffxiv.exe+101D7DF
ffxiv-exe+101FB91
ffxiv-exe+10220B7
ffxiv.exe+3C2B40
ffxiv.exe+1733BF
ffxiv.exe+10BA785
KERNEL32.DLL+1FA29
ntdll.dll+67A9E

I've tried disabling dx11 in the launch menu - didn't work.
Playing from windowless to fullscreen - didn't work.

Anyone got any idea how to fix this?