I just tried to cache an area around London City airport on high settings (photogrammetry enabled), with a manual cache size of 15 gb and had a ctd.
I tried again with an empty community folder and also got a ctd.
The cached area was no where near large enough to fill the 15 gb size of the manual cache file.
Here is a screen shot of what I am trying to cache:
Every time I try to resume download the sim crashes.
I am also unable to increase the size of the manual cache file while this download is pending.