Update to Windows 10 version 1903 stuck at 48%

Hi I have a customer's Acer Aspire E1-572G laptop that crashed overnight doing the 1903 update. So I took it back to try to do it for her since she needs the laptop for work.

This is a standalone Workgroup laptop and not connected to a domain.

I have been trying for days to upgrade this laptop to Windows to version 1903.

The update downloads to 100% and then the laptop reboots to install 1903.

Nothing external is plugged in.

It consistently freezes at 48%.

There is a single C partition so nothing out of the ordinary.

The spinning circle stops.

I have left it alone overnight but nothing changes.

I have used the Windows 10 update troubleshooter.

I have uninstalled all third party apps other than Office 2016.

I have done a disk cleanup to clear out left over files

Currently it is on 1803 so has missed the 1809 upgrade.

I have tried downloading the update through the update option as well as using the media creation tool.

However with a USB stick plugged in I get the not able to upgrade error message because an external drive is plugged in!

I don't want to do a clean install because I don't have the reg key for my Office 2016. (Jellybean can't find the key).

Anyone else with this issue and managed to fix it please?