Mac Version crashing AGAIN

GAH. I thought I had this resolved with my updating the graphics drivers, but I logged on today after a few days away, to play the Rain event, and the crashing has come back.

HOWEVER -- this time, it's happening on a very specific action.

Whenever I've been looking at the Gold Saucer vendors (the campaign or prize attendants, the ones that offer the MGP stuff for sale), FFXIV not only crashes, but forces my Mac to completely reboot.

The first time, I'd logged on fine, got out to the Saucer, checked the Campaign Prize Attendant in the Wonder room: 5 seconds after opening the window, the game & Mac crashed & rebooted.

Waited for the game to come back up, logged right back in on the same character, checked my graphics settings to make sure they were set to "Standard" (the one that seems to be for the 2013 Macs). I was still in the Saucer, and ran around for a bit, ran a couple GATEs, then stopped near the Saucer entrance and went AFK for about 30 minutes. When I came back, the game & Mac were still up & running just fine...UNTIL I opened up a nearby prize attendant vendor and started browsing the available prizes. 5 seconds later, CRASH and reboot again.

iMac 27", late 2013
Mac OS 10.12.5 (Sierra)
3.4 GHz Intel Core i5
NVIDIA GeForce GTX 775M 2048 MB
32 GB RAM, 1600 MHz DDR3

(not happening consistently, either. Just logged back in again & tried going straight to the prize vendor -- game worked just fine. GAH.)

If other information is needed, please let me know.