clean-up option fails, project is marked for deletion but doesn't delete

Using GitLab Enterprise Edition 12.9.4-ee I am able to use the tool to pre-populate data and run performance tests no problems.

When I try to clean up it fails, I have tried multiple times with different group names and they all fail. It succeeded once in a GitLab instance that is a clone of this one and the deletion seemed immediate. It seems they are being marked for deletion but not actually deleted. The groups have this message: This group, its subgroups and projects has been scheduled for removal on 2020-09-17.

My most recent run:

$ docker run -it -e ACCESS_TOKEN=token \
-v https://internal-gitlab.com \
-v config:/config \
-v results:/results \
registry.gitlab.com/gitlab-org/quality/performance/gpt-data-generator \
--environment integration.json \
--clean-up -u
GPT Data Generator v1.0.9 - opinionated test data for the GitLab Performance Tool
Checking that GitLab environment 'https://internal-gitlab.com' is available, supported and that provided Access Token works...
Environment and Access Token check complete - URL: https://internal-gitlab.com, Version: 12.9.4-ee 6a1a8e88568
Group gpttt already exists
Delete old group gpttt
Waiting for group gpttt to be deleted...................................................................................................................................................................................................................................................................................................
GPT data generation failed:
Waiting failed after 300 seconds. Consider increasing `--max-wait-for-delete` option. Exiting...
 Traceback:["/performance/lib/gpt_test_data.rb:41:in `block in wait_for_delete'", "/performance/lib/gpt_test_data.rb:39:in `loop'", "/performance/lib/gpt_test_data.rb:39:in `wait_for_delete'", "/performance/lib/gpt_test_data.rb:229:in `delete_group'", "./bin/generate-gpt-data:108:in `<main>'"]

My config file:

$ cat integration.json
{
  "environment": {
    "name": "onek",
    "url": "https://internal-gitlab.com",
    "user": "performance",
    "config": {
      "latency": "0"
    },
    "storage_nodes": ["default"]
  },
  "gpt_data": {
    "root_group": "gpttt",
    "large_projects": {
      "group": "large_projects",
      "project": "gitlabhq"
    },
    "many_groups_and_projects": {
      "group": "many_groups_and_projects",
      "subgroups": 250,
      "subgroup_prefix": "gpt-subgroup-",
      "projects": 10,
      "project_prefix": "gpt-project-"
    }
  }
}

This is annoying as I would like the test groups deleted immediately. Do you need other data/settings to troubleshoot this?