Kind of same kind of crash happened to me too a couple of days ago, though in AC19.
You might find a resolution from your library folder:
/users/username/library/preferences/MAXON/cinerender#xxxxx/illum/
or depending when or why you crashed the answer might hide in some other folder downward that MAXON hierarchy.
I tried to stop rendering with the stop button in AC19 (the red x icon). It didn't work. At that monent an endless mass-storage writing loop initiated itself. My mass storage was about to fill up quickly, so I had to force-quit AC19 and its rendering engine. My mass storage was not recovered to its earlier state. I had only little left.
So I sought thoroughly, and found out, that there was this one huge file, in size of tens of gigabytes, in the ../prefs/MAXON/ hierarchy. I deleted the file. I tested AC19 rendering. It worked fine. I emptied the trash, and all of that 60GB's came all available to me again.
ps. with newest OSX varieties you need to use "GO TO FOLDER" to get in to your library folder in finder (cmd-shift-G).
AC25, Rhino6/7+Grasshopper, TwinMotion • Mac Pro 6,1 E5-1650v2-3,5GHz/128GB/eGPU:6800XT/11.6.5 • HP Z4/Xeon W-2195/256GB/RX6800XT/W10ProWS