Checkmk API Bulk Service Discovery with mode: fix_all is not working as expected

Hey guys,
I spent the last weeks to get comfortable with the REST API, and I get along with it pretty good. (Swagger is awesome!)
Today I stumbled across something, where the API behaves really strange.
This is the curl request I run:

bulk_service_discovery_mon-client-1_company_cloud=$(curl --insecure -X 'POST' \
    --header "Authorization: Bearer automation_user $(cat /opt/omd/sites/local/var/check_mk/web/automation_user/automation.secret)" \
    'https://monitoring.local.company.toplevel/local/check_mk/api/1.0/domain-types/discovery_run/actions/bulk-discovery-start/invoke' \
    -H 'accept: application/json' \
    -H 'Content-Type: application/json' \
    -d '{
    "hostnames": [
        "mon-client-1.company.toplevel",
        "mon-client-2.company.toplevel"
    ],
    "mode": "fix_all",
    "do_full_scan": true,
    "bulk_size": 10,
    "ignore_errors": true
}')
echo -e "Execute Bulk service discovery with fix_all.\n"

After running this, the services on the two hostnames I provide get discovered, but they do not get added (like the mode fix_all suggest), I don’t get any changes afterwards for added services or updated tags, etc.

However, running the service discovery via a curl request on https://monitoring.local.company.toplevel/local/check_mk/api/1.0/domain-types/service_discovery_run/actions/start/invoke they get discovered and added to changes - how I want it to behave:

service_discovery_mon-client-1_company_cloud=$(curl --insecure -X 'POST' \
    --header "Authorization: Bearer automation_user $(cat /opt/omd/sites/local/var/check_mk/web/automation_user/automation.secret)" \
    'https://monitoring.local.company.toplevel/local/check_mk/api/1.0/domain-types/service_discovery_run/actions/start/invoke' \
    -H 'accept: application/json' \
    -H 'Content-Type: application/json' \
    -d '{
    "host_name": "mon-client-1.company.toplevel",
    "mode": "fix_all"
}')
echo -e "Run discovery for mon-client-1.company.toplevel with fix_all.\n"
service_discovery_mon-client-2_company_cloud=$(curl --insecure -X 'POST' \
    --header "Authorization: Bearer automation_user $(cat /opt/omd/sites/local/var/check_mk/web/automation_user/automation.secret)" \
    'https://monitoring.local.company.toplevel/local/check_mk/api/1.0/domain-types/service_discovery_run/actions/start/invoke' \
    -H 'accept: application/json' \
    -H 'Content-Type: application/json' \
    -d '{
    "host_name": "mon-client-2.company.toplevel",
    "mode": "fix_all"
}')
echo -e "Run discovery for mon-client-2.company.toplevel with fix_all.\n"

I don’t know if I miss something (I guess I do), but I just spent time to get this running and couldn’t make it work.