Windows 7 to Windows 10 upgrade, glitch on outlook signature image

We recently upgraded a couple of machines in our office to Windows 10 version 1909 from Windows 7. These both had Outlook 2013 installed during the upgrade.

After upgrading (and installing the latest graphics drivers) the email signatures that show when composing a new email or replying have glitched. Instead of showing the correct images in the signature, it just shows a random snip of the screen.

We tried uninstalling and re-installing Outlook with office 2013 and even tried to install the latest version of office 2016 with the same result. We also re-installed graphics drivers, and remove and re-added the user’s outlook profile. This only occurs when writing an email, and only when the signature is applied. If sent, the emails display fine to the recipient.

I also tried disabling hardware-accelerated graphics, but this caused outlook to display completely wrong, just showing white for most of the window. I had to edit the setting in the registry to get it to change back as I couldn’t open the options menu after that.

Our email signatures are deployed with a tool called Exclaimer Signature Manager Outlook Edition, which has worked fine with windows 7 in the past and is working fine with at least one other PC that was upgraded to Windows 10 in the same way.

Had anyone seen this before or know anything else I can try?