Umb 7.15.3 (upgraded from 7.3.8)

Importing data from a working API with the following code.

var cs = ApplicationContext.Current.Services.ContentService;    
cs.Save(nodeToPublish);
cs.PublishWithChildrenWithStatus(nodeToPublish, includeUnpublished:true)

It hangs on the third line and gives a timeout or server not responding exception. However the site saves and publishes correctly when done manually via Umbraco, so the server connection is good and responsive. The code hasn't been changed since it was working on V7.3.8. I don't see anything obvious when comparing the code to the docs.

Any advice would be appreciated.

Rgds

Craig

PS I know this should be in "Extending Umbraco and using the API" section but the UI confounded me, twice. :(