Hey there,
Whenever I use Teamviewer to remote to my workstation and I from there have to use Remote Desktop (MSTSC) to access a server I have issues with alternate keys not being sent across to the server. Ctrl, alt and Shift keys aren't working on the server, but they are if I access the server directly from my workstation when I'm physically in the office. So I can only type lower case and have issues with any copy pasting etc. whilst on the server.
Using Teamviewer 15.8.3 and Windows 10 / Windows Server (several versions)