Not sure if the entirely same issue but in a similar vein to the others at seemingly completely random intervals (Whether in or out of a duty, in or out of combat, temporarily idling or actively playing) the entire game will lock up, I've had it not happen an entire day and then earlier today it occurred twice within the same fight (final boss of the final Main Scenario Dungeon, though uncertain if that is relevant)
Unlike the others mentioning crashes this does NOT crash my game but does cause it to become completely unresponsive for what feels like ~15-30 seconds (checking Task Manager shows the program as unresponsive and the CPU/GPU usage values drop to 0 or near-0 values)
No error message occurs, a browser (Firefox) and Voice Communication (Discord) have been running during these, although they were also running prior to the DT update and this issue never happened prior