Hi Absentnoob666,
Thank you for reaching out to Microsoft Community. We are sorry to hear about what is happening to your Surface Pro 5thgen.
We need to isolate first what may have caused the issue. Please follow these steps below:
Go to Windows Settings > System > Storage, please check what are the things that is taking up the space on the drive.
If Temporary files are taking too much space, type %temp% on the search box at the left side of your Taskbar then hit Enter.
Other way to open your Temp folder :
Open File Explorer > This PC > Windows C > Users > choose your User folder
Click View on the upper part of the File Explorer then check the box for Hidden items
Look for AppData > Local > Temp
Check what are those files being stored in your Temp folder.
If you are seeing a lot of files named "AppXDeploymentServer….", please type Powershell on the search box left side of your Taskbar.
Right-click on the Windows Powershell app then choose Run as administrator. Click Yes on the prompt.
Type the script below and hit Enter:
Get-AppxPackage *Microsoft.SurfaceHub* | Remove-AppxPackage
After that, go back to the Temp folder and Delete all those files inside the Temp folder.
After deleting, please update your device.
If this answer your question, we highly encourage you to inform our Community by clicking on Yes or marking my post as an answer. This will help other members who may have the same issue as you. Otherwise, don't hesitate to update us so we can further assist you.
Kind Regards,
Marrion Y.