I would look further look into the namespace that is required to reach the saved search you are trying to disable.
https://docs.splunk.com/Documentation/Splunk/7.2.3/RESTUM/RESTusing#Namespace
As most likely is that the rest endpoint either doesn't have access to that search or is just creating a new search that its disabling automatically but is never hitting the originating saved search.
If this saved search name is unique an easy way to edit this search is by the following command:
curl -k -u admin:pass https://localhost:8089/servicesNS/-/-/saved/searches/TestSearch/ \
disable -X POST
As this will be looking over over all levels of access (private,app,global) for the saved search that matches TestSearch.
... View more