I recently upgraded an Umbraco instance from v7.2.8 to v7.4.3 and as a result Courier has stopped functioning correctly.

The deploy process functions correctly, right up until the collection phase after which the interface freezes, as can be seen here:

At this point we receive the following browser console error:

VM1990 RevisionJsonRender.js:12 Uncaught ReferenceError: g is not definedupdateCurrent @ VM1990 RevisionJsonRender.js:12(anonymous function) @ VM1991 CommitItem.aspx?providerGuid=d8e6ad83-e73a-11df-9492-0800200c9a66&itemid=a83b3dfa-35f3-40c5-…:91

And this message twice in the Courier Trace log:

ERROR Umbraco.Courier.Core.TaskManager - [Thread 48] Error PackagingTask with id: 13b0086f-d90e-4a1a-967d-c6338c46ec3c
System.Web.Services.Protocols.SoapException: Server was unable to process request. ---> No provider<Umbraco.Courier.Core.ItemProvider> with id '177e3cf9-2d0b-42b8-9d7d-a9ccb2439a4d' found
   at System.Web.Services.Protocols.SoapHttpClientProtocol.ReadResponse(SoapClientMessage message, WebResponse response, Stream responseStream, Boolean asyncCall)
   at System.Web.Services.Protocols.SoapHttpClientProtocol.Invoke(String methodName, Object[] parameters)
   at Umbraco.Courier.RepositoryProviders.WebServiceProvider.RepositoryWebservice.GetItemHash(String sessionKey, ItemIdentifier itemId, String user, String pass)
   at Umbraco.Courier.RepositoryProviders.CourierWebserviceRepositoryProvider.Hash(ItemIdentifier itemId)
   at Umbraco.Courier.Core.Packaging.RevisionPackaging.Package()
   at Umbraco.Courier.Core.Tasks.PackagingTask.Run()
   at Umbraco.Courier.Core.BackgroundTaskRunner`1.ConsumeTaskInternal(T task)

I have upgraded Courier from v2.52.3 to v2.52.4 with no change in behaviour.

Any help on where to even begin would be greatly appreciated.

Kind regards, Chris