This started with the latest HB update. to me it only happens with GB2. It's REPRODUCIBLE, and happens a lot in deepholm and vash'jir.
Here's the situation:
Bot tries to get to a node that either HIGH UP on the edge of some mountain in deepholm, or obstructed by some overhang, doesnt quite reach it, bounces all the way down again, does this a few times and bam, blacksreen. stop bot, relog, char is just there doing nothing special. if you start again, blackscreen again. similar situation with vashjir and mountains / coral obstructions. if you try to move manually during blackscreen client DCs to login screen or sometimes just crashes.
There are NO ERRORS or anything special in HB log. wow crash log is error 132.
Here's the solution till devs fix the program: every time you get blackscreen, log back in and blacklist a large area around that node. that's it. otherwise next time the bot comes around to this node, it will crash again.