Windows 10 Update using SCCM to 1903 Timing out

I work for a school. In preparation for the summer, I am investigating methods of updating our installed versions of Windows 10 1709 to something more current. I'm thinking it's either going to be 1809 or 1903.

My preferred method would be to use the Windows 10 Servicing Plans inside SCCM. I have created some collections, downloaded the required updates from WSUS and put them into SCCM, created a servicing plan, created a package to put the resulting updates into, distributed those packages to the DPs and deployed the servicing plan to my collection. The clients which are members of that collection then pick up the deployment and start to install the OS update. So far, so good.

The issue is that with the VMs I've been testing it on, the installation fails after an hour with an error code which suggests that the process is timing out. The SCCM console also reports that it's timing out as well. I have gone to the properties of the update in the SCCM console and changed the Maximum Run Time from 60 to 360 minutes but the installer still kills itself after one hour.

The setup routine generates a large log but the pertinent part of it appears to be this:

2019-06-07 09:48:40, Error                 MOUPG  CSetupHost::OnProgressChanged(2126): Result = 0x800704C7
2019-06-07 09:48:40, Error                 MOUPG  CSetupManager::DlpManagerCallback(2008): Result = 0x800704C7
2019-06-07 09:48:40, Info                  MOUPG  Remapping ERROR_CANCELLED to ERROR_REQUEST_ABORTED
2019-06-07 09:48:40, Info                  MOUPG  Cancel of current task requested...
2019-06-07 09:48:40, Info                  MOUPG  Attempting to cancel current task...
2019-06-07 09:48:49, Info                  MOUPG  MoSetupPlatform: Calling SetupPlatform::INewSystem::RequestCancelOperations...
2019-06-07 09:48:49, Info                  MOUPG  Task cancel request returned: [0x0]
2019-06-07 09:48:49, Error                 MOUPG  SendCallbackMessage: [0x7] -> user callback returned 0x800704D3
2019-06-07 09:48:49, Error                 MOUPG  CDlpTask::Cancel(984): Result = 0xC1800108
2019-06-07 09:48:49, Info                  MOUPG  SendCallbackMessage: [0x7] -> Cancel request returned 0xC1800108

The timestamp on the logs is exactly one hour after the installation starts which suggests the installation is timing out.

The SCCM console reports the following:

Reinforcing that suggestion. I've Googled that error code and all of the results that I've found said that I need to increase the maximum run time from 60 minutes. However, the maximum run time on the update that it's trying to apply is already 360 minutes:

and that has made no difference, the update installation is still killed after one hour.

I could use a task sequence to update the operating system; I've been testing this method and that works. However, I'd prefer to use the servicing plans as I think the dashboard for it would be useful.

I'm not sure what I've missed and I would appreciate any suggestions people have.