Question about Office365 Shared job results folder

I have a question about the Shared Job Results folder as used by Office365 sharepoint.

Here is my setup:

2 access nodes, call them N1 and N2

Both Access nodes have a Job results folder set to its own local local dedicated drive which is 150GB in size. 

In the Sharepoint client I have configured a shared job results folder on a CIFs share that is 1 TB in size and both N1 and N2 are added as access nodes successfully. 

 Here is the issue:

When I perform a backup of sharepoint I notice the access nodes local job results drives get used and fill up causing some failures of sites and subsites in the backup. I notice the shared folder barely gets used, but it does get used. The error reported for the failed sites is “Space Control Job level timeout 60 minutes”

Am I missing something, do I need to manually point the 2 access nodes Job results directories to use the shared folder manually as well? Or do I just need to grow the local drives. I am not sure I understand why the shared Job Results folder isn’t used more.