Description:
When trying to save changes you have to a diagram via the web server (Web authoring) within TIBCO Nimbus - you may get an error "Failed to Save the current diagram"
Symptoms:
"Failed to save the current diagram" error
Cause:
WebDAV is installed on the server - This component is explicitly referenced as a not-required component and should be uninstalled from the IIS instance hosting the webserver.

WebDAV can be disabled on a per site level but that falls outside the scope of this knowledge base and is not a supported action as WebDAV is excluded directly in the application Administration Guide and the Installation planning guide which can be found here:

https://docs.tibco.com/products/tibco-nimbus-9-5-1