When you are connected in a remote session, you may get letters that are typed in uppercase or the letters may not be typed at all.
1. Please connect to the computer and click the Actions icon in the toolbar at the top of the screen.
Then, change the 'Keyboard Mapping' to another option and see if there is any improvement. If it is set to 'Splashtop Mapping', please try adjusting to 'Alternative Mapping'. If it is set to 'Alternative Mapping', please try adjusting to 'Splashtop Mapping' and check if there is any difference.
2. Please try rebooting either end or both computers.
3. If rebooting didn't help, it could be due to a buggy Streamer so uninstalling and reinstalling the Streamer should help resolve the issue. You can find the uninstall link here and the reinstall link here.
4. If the issue still occurs, please try unplugging and replugging the keyboard in on either end or both computers.