Request Timed Out (submission on sample_set entity with 8891)

I have a WDL and a method configuration for it. The root entity type of the configuration is a sample_set.

I have two submissions from this configuration on a sample_set. The number of samples in the sample set is 8891. The WDL calls first for a "scatter" whose width is equal to the number of items in the sample set. Then, a single "gather" step takes in an array from the scatters to "gather" them.

The two submissions are referenced here where you can see the workspace name and submission ID.

https://portal.firecloud.org/#workspaces/broad-firecloud-testing/hg38_PoN_Creation_copy/monitor/bbf0ecec-a742-4749-804c-9e390035b3ba/98ac216e-7e26-4cb2-b74e-84df71e63e79

https://portal.firecloud.org/#workspaces/broad-firecloud-testing/hg38_PoN_Creation_copy/monitor/fc3108b0-abcf-41b9-b273-5652f02439b7/903efa1a-1ebf-4246-81b0-4f3339f3ead5

For both submissions (from already being in the monitor tab) when I go to the submission in the UI I get a message:

Server Unavailable
FireCloud service is temporarily unavailable. If this problem persists, check http://status.firecloud.org/ for more information.

While trying to do so I have my console open for the network tab and there I see:

{
  "statusCode": 504,
  "source": "FireCloud",
  "timestamp": 1506518502605,
  "causes": [],
  "stackTrace": [],
  "message": "Request Timed Out"
}

For other submissions I encounter no error message and I can enter them in the UI no problem.

It seems that there's a timeout and based on previous experience I speculate that the timeout is related to the size of the sample_set (8891) because for the same WDL I can view submissions on sample_sets with smaller size (1) without encountering any problems.