A problem since Windows Vista was launched is that when you remote control another user and try to elevate to Administrator, using for instance Quick Assist which is built into Windows 10 or TeamViewer, the screen on the admin side will freeze. This is due to UAC Secure Desktop feature kicking in.
The solution is to turn this secure desktop feature off, lowering security a little but at hardly no risk.
Configuration via Intune (MDM)
Create a Configuration Policy > Endpoint Protection and go to Local device security options > User account control. Set the setting Route elevation prompts to user’s interactive desktop to Enabled.
Configuration via Group Policy (GPO)
In the GPO editor, go to Security Settings > Local Policies > Security Options > User Account Control: Switch to the secure desktop when prompting for elevation to Disabled